Name any genre of music and associated subculture, any, and flame wars will ignite. Particularly volatile topics are: what is acceptable as heavy metal, which school of blackmetal is true/kvlt and how to 'define' goth.
Mentioning that you like The Smashing Pumpkins is a good way to make some people ramble madly at how you are a fifteen-year old girl who thinks that they're deep and intelligent or a fratboy douchebag who likes to slip roofies into drinks and commit date rape.
Most of the most well-known figures of Visual Kei and anything relating to them or their acts. Yoshiki Hayashi, Dynamite Tommy, and Gackt all have many associated flamewars, for example - and gods help you if you get into the meta-wars of who among them is the best artist in Visual Kei. Yoshiki vs Gackt, specifically, will lead to outraged fans of both screaming at each other, spreading rumors, and a possible literal dick-measuring contest. Yoshiki vs. Dynamite Tommy actually once led to a literalFlame War that burned down a bar. Gackt vs Mana is another big one here, where both sides in this one often think the other is an egotistical band-destroying Jerkass.
Gackt's tabloid rumors have become a Flame War industry almost. Dears arrive to insist the scandal is entirely false. While anti-fans will insist the story is true despite any evidence. The scandal involving rape charges caused a huge flame war that eventually died out win he was found innocent of all charges.
Beneath The Skin. Who sings better, Gackt or Toshi? Is not including an uncredited vocalist "stealing his song?" How much work does a remix have to undergo to be considered a new song anyway? This song, if mentioned around a place where there are fanatical X Japan fans/Yoshiki fans and fanatical Gackt fans, is the Flame War equivalent of thermite.
Dir En Grey. ANYTHING related to Dir En Grey. Most Visual Kei bands (or ex- Visual Kei bands) have a specific set of Berserk Button that, as long as you don't touch them for any reason, you will be relatively unscathed. Dir En Grey has nearly everything as a potential Berserk Button for someone somewhere in the fandom. Individual fans aren't necessarily a problem, but almost every community for the band is a Flame War minefield with some people who will see anything as personally enraging enough to literally cyberstalk you for years, rain down the most venomous verbal abuse possible, and even go out of their way to attack other fans in Real Life at shows.
The Tokyo Damage hit piece slamming Visual Kei as a dead genre of sellouts and sexually confused people, citing one burnt-out person's experience as a producer, and accusing all Visual Kei artists of being yakuza criminals. The piece was actually removed from Tokyo Damage itself when it failed a fact check (for, among other reasons, the lack of more than one source on its allegations), several of the parties named (including Yoshiki Hayashi and Dynamite Tommy) allegedly threatened libel suits, and the homophobic and transphobic nature of the snark began to be repeatedly called out, but it was uploaded elsewhere and took on a life of its own. Those who post the piece to troll (or who just find it and are unaware of its history) will insist that it is the utter, hard truth of the reality of Visual Kei, and will spread conspiracy theories that the removal of the piece was due to the Yakuza (and not due to that it was a factually inaccurate, libelous, and offensive rant), which draws the expected reaction from the insulted parties and their fans. The real fireworks happen when it gets posted somewhere containing active indies Visual Kei artists who actually do read English well enough to understand the English-only article.
Whether any given band or artist has sold out, whether their older or newer stuff is better.
"Are those guys or girls?"
Any discussion of bandslash or sexuality of artists at all. And yes, this applies even if the artist(s) are out and proud as gay or bisexual - somehow it is seen that out GLBTQ artists need more "privacy" and "discretion" in discussion than heterosexual ones, and that GLBTQ groupies or fanboys/fangirls are somehow more offensive or "disrespectful" to the artist for expressing feelings that would be at worst giggled at if expressed by cisgendered heterosexuals. Even if the artist and other artist or groupie/fan's orientations are compatible.
And a very, very nasty meta-flamewar can be started by mentioning those exact applications of the Double Standard for expressions of heterosexual desire versus expressions of same-sex desire, and/or by mentioning that perhaps some people involved in Visual Kei may not be fully and entirely cisgender off the stage.
The circumstances of the death of pretty much any Visual Kei artist that has died. hide, Jasmine You, Isshi, and Taiji especially attract this as in their deaths were mysterious and/or suspicious, and if people who think they were murdered/there was negligence around their deaths end up in the same place as people who are insistent on their deaths being uncomplicated suicides, there will be Flame War.
Visual Shock/Veteran Kei OR Black Kote Kei or Eroguro Kei vs. Oshare Kei. The former three genres are mostly made up of varying forms of Hard Rock and Heavy Metal to, in the case of Eroguro Kei, extreme metal and black metal. Oshare is pop, pop-punk, with some lighter EDM. The metalheads tend to hate the poppy, light, commercial-friendly sound of Oshare and the "cuteness" of the style, and loathe it for invading a style founded in hard rock and heavy metal, where the Oshare fans tend to see the metalheads as holding onto the past and negative/dark/not cute and cool, and often think Visual Kei should be more "cool kawaii Japan."
This one can go Up to Eleven when the Oshare band is obviously unskilled/untalented and yet has a ton of expensive costuming/gear/production/etcetera, because then it becomes class warfare and jealousy as well - since as of The New Tens most of the HR/HM leaning bands and artists (aside from the obvious exceptions like X Japan and Dir En Grey) are nowhere near rich. The reaction of people who can barely afford their gear or paying for a venue to a band that can barely play despite their top of the line gear getting top billing and tons of press is... often slightly angry.
In a similar but worse vein, Korean Pop versus Visual Kei. This one can draw a wide variety of flames ranging the entire Sliding Scale of Idealism Versus Cynicism - on the more "idealistic" side (or the more sympathetic one) you have the same situation as the metal subgenres versus Oshare - a simple conflict over genre. On the more cynical side, you have Unfortunate Implications gone wild, with Japanese, other Japanese, Westerners, and Koreans all flinging extreme racist abuse at each other and denouncing whatever side they hate not out of genre distaste but out of overt racism and Misplaced Nationalism.
Hiroshi Matsumoto giving the rights to cover hide's image song Pink Spider to Koda Kumi produced a short Flame War mostly directed at him and/or Koda Kumi for the result being generally recognized as crappy. It also slowed the crossover between Visual Kei and pop to some degree.
Hiroshi Matsumoto in general is a living Berserk Button. While he has his defenders, his obsession with turning hide into a Cash Cow Franchise has alienated much of the hide fandom from openly expressing support or admiration for him at the very least and has turned a fairly large portion of it (especially the English-speaking fandom) directly against him. It doesn't help his case that anyone who looks into hide's death and surrounding events at all will find Hiroshi to have at least been a negligent Pointy-Haired Boss of a manager (and some even allege him to have been the Heteronormative Crusader who let hide's problems consume him on purpose since that was easier than dealing with him/managing his reputation somehow alive), and that he became most widely known for engaging in protracted and pointless legal battles over hide's image, while stealing fan art to make it official LEMONED products, with the lawsuits only stopping when he filed a Frivolous Lawsuit against Yoshiki Hayashi for using hide's image in X Japan, the band that had made hide famous, and Yoshiki fought back rather than paid up. While not everyone hates him, any of the above can lead to a Flame War, although one usually closer to an Internet Counterattack against him, and he arguably sports the one of the biggest Hatedoms of anyone in Visual Kei, to the extent that there's active campaigns to defund the Cash Cow Franchise by fans sick of the way he's managed hide's estate.
Old school rap 80s and 90s vs. The new stuff. The discussion starts off civil enough, then everything goes to hell. Exemplified by fans of the new stuff calling the other group a bunch of old out of touch whiners with a Nostalgia Filter, and the former calling the latter group a bunch of white kids pretending to be black over the internet, or a bunch of suburban/dumb girls/uncle toms etc who like popcorn Glam Rap cause they can't hack real serious Hip Hop. It has gotten real personal in some cases, even outside the internet.
Don't forget East Coast vs. West Coast. Or more cynically New York vs. everyone else that isn't New York. New Jersey might be an exception..maybe.
Or rap vs. other genres of music in general.
There's also those who judge artists solely on "relevance" rather than talent and credentials. This applies to music ingeneral as ewll.This also further divides fans.
Korean pop is quite notable for having several different opportunities for flame wars. Did SNSD or SJ deserve to win the Daesang? Maybe it was 2NE1? Is 2NE1 better than SNSD/4Minute/Miss A/etc.? Is this singer/group talented or just a bunch of useless plastic sluts?
Are Yoona, Yuri, Sooyoung and Hyoyeon useless or do they provide flavour in SNSD?
Are idols like Dara, Yoona, Sohee, Hwayoung, etc. useless in their groups or do they simply have "fresh" voices?
Is 2NE1's CL the "baddest female Seoul City ever had" or is she a shouty, nasal-voiced tryhard who could never compare to the likes of Tasha?
Just how much should a female idol weigh? Should male idols show their abs? How much skin is too much? What's too risque?
Did Rania actually bring something fresh to the k-pop scene, or were they too over-exposed and "slutty"?
Is 2NE1 more about the music or the style?
TVXQ. Do you support JYJ, Homin, or both?
SONES vs. STAND. There's also any of the fanclub wars, which have a tendency to go supernova very quickly.
How many members of Super Junior should there be?
There's also what inevitably happens if a male idol gets a girlfriend - one side will flame her, send her hate letters/death threats and hurl abuse at the male idol. The other side will say "Hey, why not let them be happy?" The flamers will then retort "Well, you're OBVIOUSLY not a TRUE FAN", and things will degenerate from there.
Plastic surgery. Does this invalidate a singer's talent? Are the male idols who get it better than their female counterparts?
Comparisons of Opera singers, especially dead ones, can spawn enormous flame wars among enthusiasts. Ask an opera buff on his opinion of Maria Callas vs. Renata Tebaldi or Mario Lanza vs. Jussi Björling. Or just read the comments to some opera clips on YouTube.
My favorite violinist vs. yours. Period! Go to any Youtube video on any virtuoso and just see the comments unfold below.
Justin Bieber's "Baby" video had been flamed by an internet group The "Metal Militia" on September 1, 2010. Bieber himself has taken a lot of fire for his popularity and appeal with young girls, and, in the eyes of some, mediocrity as an artist. As of recent months, he's attracted even more ire for his immature handling of his brushes with the law (particularly his DUI arrest in January 2014) and several downright strange public gaffes (such as claiming Anne Frank would be a Belieber).
In the Vocaloid fandom Kagamine fans are known for really long arguments over whether the two are twins, lovers, both, or each other's reflection in the mirror.
Jazz. The entire fanbase more or less split wide open in the 80s, with one side embracing the more commercialized aspects of jazz-rock fusion and smooth jazz introduced in the 70s, while the purists vehemently hating them. These days, smooth jazz generates ire from either side of the fence, but the purist debate on what jazz is supposed to be rages on.
Jazz split many times before the 80s. Bebop was controversial when it first came out, and Bossa Nova made jazz safe again for the mainstream. Then you have free jazz, which still has its detractors. And jazz fusion...
Indian music - Tradition vs. Innovation. Religious vs. Non-religious themes. "Authentic Performance" of ragas and compositions. Commercialization. Raise any of these and you're just asking for it.
Far worse in the previous half of the century, although debates still flare up on any subjective topic.
Tradition vs Innovation is staple of any form of classical music.
Any genre of classic music - Four words. Historically Informed Authentic Performance. Opinion wars have been known to end up more hysterical than historical.
Nightwish has HUGE flame wars over whether Tarja or Anette is the better singer, despite the fact that Tarja left over six years ago. The war is still going strong.
Green Day: Either anything after Dookie is bad, or only their new stuff is good, or anyone who likes American Idiot is a noob and a sell-out, or anyone who likes 21stCenturyBreakdown is also a noob and a sell-out, or if you like the band period, you're a fag who doesn't listen to "real" rock music.
Pop-R&B vs. straight forward R&B. Some thinks that regular R&B doesn't even exist on mainstream radio anymore because of Pop-R&B. The flames come from arguments on whether or not the former pop artists are good singers, and or manufactured. Alternatively does that even matter and are the complainers out of touch?
Richard Wagner's music is incredibly divisive among fans of opera and classical music, evoking massive levels of Love It or Hate It. (It doesn't help matters a bit that, aside from his already controversial music, Wagner also wrote some nasty anti-semitic tracts. And, even worse, he was reportedly the favorite composer of a certain German dictator, so Godwin's Law is built right into the discussion.) One music historian remarked, "I never discuss politics, religion, or Wagner. It always makes for bad blood and originates quarrels."
My Chemical Romance. Oh sweet, sweet God. To name just a few: Everything after Three Cheers For Sweet Revenge is lame and not rock music. No it isn't, The Black Parade is a fantastic album, but Danger Days is popularist trash. No it isn't, I haven't even bothered to listen to the first three albums, but Danger Days is amazing. MCR write rock music. MCR DO NOT WRITE REAL ROCK MUSIC, they are emos. MCR hate the emo label, they even say so themselves, they're really goths. MCR aren't goths, they're stupid posers. MCR aren't anything, they just write what they like when the mood takes them! MCR are a Goddamn suicide cult! MCR fanfiction is hot when it depicts everyone having sex all the time. MCR fanfiction is weird and creepy. MCR and everything about them sucks ass! MCR is the best band ever, ever, ever, period. And the list goes on.
If you go on a Beyonce video and say that another singer sings better, it won’t end well for you.
There's other shades of this as well. For example people might acknowledge Bey as a great performer, and entertainer but would stop way short of calling her a great singer.
In many cases where a band might replace a member for any variety of reasons, arguments will ensue.
Arch-Enemy: The Michael Amott fans versus the Angela Gossow fans. It can get especially fiery when the gender card gets pulled out.
Escape the Fate is infamous for its enormous Broken Base with regards to whether you prefer original singer Ronnie Radke or second singer Craig Mabbitt, even though both parties have already moved on, and Ronnie has his own band to front. The comments on their Youtube videos will devolve into some downright ugly flame wars within minutes. It even carries on over to their Facebook pages.
X Japan has three of them, two of which invoke Dead Artists Are Better and the other one which does so indirectly. Taiji vs. Heath on bass, hide vs. Sugizo on guitar, and whether Sugizo was the right choice to replace hide. (For example, some Kaoru and Miyavi fans still think Kaoru or Miyavi would have been a better choice than Sugizo.)
The mere mention of a certain Evanescence song is enough to cause waves of internet backlash, particularly if it's mentioned on the official Evboard. Some fans believe You is a deeply personal song Amy never intended to release, so much so that it's been awarded the term Forbidden Song. Asking about it will often result in much bile being spat your way.
Whether or not Eminem's success is mostly due to talent, or because he's a white rapper. note Although to be fair most of his detractors still acknowledge his talents though. Eminem himself doesn't doubt this claim, his white fans on the other hand..
Some take a third option and say it's both race AND talent. Others have also claimed there is a media bias regarding how they cover his as oppose to other rappers.
Current-day Eminem also tends to inspire a lot of debate. Some people say he's just going through a Dork Age, others say that he's a washed-up shadow of his former self relying on his name who does shit that he wouldn't have dreamed of doing in his prime and who now makes disposable pop music and ringtone fare that just barely qualifies as hip-hop.
Any time there's a top 10/20/50/100 greatest singer/band/group/song/rapper/album/musician or whatever list, expect nuclear fallout over who made the list, or didn't make the list, and the order of the list. Especially if the top 10 of the list contain a lot of current crossover pop artists.
Due to the artist page system of Last.fm, bands sharing names have to share pages; if either band is popular, you can bet there will be flamewars, mostly over who should get the image for the artist page or the top artist biography.
Pretty much any star singer/rapper who used to perform "underground" that shoots up to popularity suddenly will have a Broken Base of people who think they are fake (often these are the most vocal) to the new fans who think they are better now and everyone else has a Nostalgia Filter.
It doesn't really have to be underground artists. It could also be mainstream artists that suddenly crosses over to "pure" mainstream. The reality of the situation is that artists rarely crosses over with their style and identity remaining intact. Things tend to get lost with the cross over that's just the nature of the beast. That's why core fans are hostile of cross over success, cause they fear that it means the artists has to give up what the fans liked about them. It's also more complicated then just simple "Nostalgia", If anything it's more so Pop-Culture Isolation. Especially with genres like Hip Hop, Heavy Metal, Hard Rock, and Country Music. Pop doesn't have to worry about this because well... it's pop music. The aforementioned genres have a harder time being accepted by the mainstream. So when they cross over they bring in new groups of fans, usually different from the core. These groups rarely gel well , and it's like mixing two volatile chemicals together.
Nightcore, though it's not really a music genre. It's more of a viral Internet trend that involves speeding songs up in order to make them sound more happier, originating from two boys in Norway who sped up techno/dance songs. As more and more people began to create nightcore of their own, debates on various topics began to emerge. As said before, nightcore is not considered to be a music genre, but there has been debate over whether or not it should be its own genre. Another hot topic that causes a lot of arguments are whether or not sped up non-techno music should also be considered as nightcore.
Like the Hip Hop genre Metal, (and its offshoots) are a cause of Love it Or Hate it flame wars. It's either the most greatest and significant genre ever ever conceived by man, Or a genre that's fueled by rockism (or metalism in this case), and is nothing more than loud noise with guitars tuned to sound like chainsaws with no rhythm or melody, and with lead singers that sound like the cookie monster.
On that note, Metallica: Did they sell out during the 90's or simply evolve? To be fair, this debate seems to have subsided more-or-less after the release of "St. Anger" (an album people on both sides hated). But, particularly around the turn of the millennium (ie. post-Napster), just mentioning the name in a music-themed forum could spur some massive flame wars.
Some people think Michael Jackson was the greatest pop star the world had ever known, and a true humanitarian to boot. Others thought he was an overly-commercialized pop singer... and that he was a pedophile. How could any of this lead to a flame war?
In the pop arena it's, rampant waring on skills, work ethic, relevance, popularity, mass of fanbase, rabidity of fan base, vocal skills, frequency of touring, whether they made the feature better or was the little side feature in a song, what counts as a hit or a #1, whether they're artist flopped or not? Pop fans are nuts.
Delta Goodrem fans are contentious about how mad fans should be or stay about Brians involvement in her life, her work ethic, her follow through, Delta 07 is an issue, how hard and how to approach The Americas and Europe?
Norwegian folk music. Do NOT try to discuss "authenticity" with anybody. A dramatic example occurred when a certain valley began to debate exactly how to dance their traditional dance. This particular discussion turned epic, and is referred to as "the war of how to bounce on the second beat"...