->'''Randal''': Which did you like better? ''[[Film/ReturnOfTheJedi Jedi]]'', or ''Film/TheEmpireStrikesBack''?
->'''Dante''': ''Empire''.
->'''Randal''': Blasphemy.
--> -- ''Film/{{Clerks}}''

Among {{Fandom}} there are some topics which, once mentioned, [[InternetBackdraft will cause endless, passionate debate]] over which [[BrokenBase faction of the Fandom]] is correct. Then there are some things which it seems like ''everyone'' in the {{Fandom}} agrees on. ''Of course'' Creator/AlanMoore is one of the best comics scribes out there. ''Of course'' the American adaptation of ''Series/{{Coupling}}'' sucked. And ''of course'' ''ComicStrip/{{Garfield}}'' has been [[JumpTheShark going downhill]] for years. How could anyone think otherwise?

Well, inevitably there are one or two fans who do. Actually voicing these opinions which run contrary to {{Fandom}} consensus, however, can entail some risk. You might get some funny looks if you said you preferred the Japanese ''Anime/GoLion'' over the American ''Anime/{{Voltron}} Lion Force''. If you say you liked ''Voltron Vehicle Force'', however, prepare to be treated as a {{Fandom}} pariah, along with comments that [[NoTrueScotsman you're obviously not]] a ''real/true'' fan. Essentially, this is the {{Fandom}} variant of TheComplainerIsAlwaysWrong.

Sometimes, this trope can even extend to fans who hold opinions that are only tenuously related (or, in some case, ''entirely unrelated'') to the work in question - which run contrary to {{Fandom}} consensus. Can exist in the form of "you can't be a true fan of Band X, if you [[FandomRivalry also like]] [[FanHater Band Y]] or you [[ComplainingAboutPeopleNotLikingTheShow don't also like Band Z]]".

By the extension of the above two paragraphs, in certain circles, the term "true fan" is the fandom equivalent of GodwinsLaw. It's like declaring "I believe in X because I'm a 'regular' fan". In other words, if someone plays/invokes the "X because ''I'' am a [[NoTrueScotsman true fan]]" , then they automatically lose the argument.

->"After a rather influential message by M Sipher in 1997 the term 'true fan' has taken on a whole new meaning among some [=TransFans=]. It's a sort of twist on Godwin's Law where anybody who accuses somebody of not being a true fan automatically loses any argument, and is often discounted as a buffoon afterwards."
-->--'''Steve-o's Transformers FAQ'''

'''Please note, to count as Fandom Heresy it must be said by someone who ''is'' part of the {{Fandom}}.''' For example, someone saying "{{Anime}} is stupid" or "''Literature/{{Discworld}}'' is boring" doesn't count. However, an anime fan saying, "Creator/HayaoMiyazaki sucks" or a ''Literature/{{Discworld}}'' fan saying, "Sam Vimes is the lamest character in the series" would definitely count.

A very commonplace, fandom-independent example of Fandom Heresy is disliking the main character, or the EnsembleDarkhorse if the main character isn't also the most popular character. Doubly so if you say that said character is a copy of a character from another series. Being a fan of TheScrappy is just as universal an example of FandomHeresy, for equally obvious reasons.

See also FanDumb and InternetBackdraft for another way to hit the BerserkButton of certain fandoms. Compare with BrokenBase, where the two sides of opinion are more equal rather than one overwhelming majority against a minority "heresy"; as well as SacredCow, in which the "heresy" includes even non fans.

'''''No examples, please.''''' What might be considered to be something "everyone" within a fandom is supposed to like often relies on personal opinion which can lead to heated debates, [[Administrivia/RuleOfCautiousEditingJudgement and we're not really too keen on having that here.]]