These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Gunnery Sergeant Hartman was either just doing his job and honestly trying to prepare his trainees for war, or his methods were so unnecessarily extreme and brutal that they drove one of his cadets to madness and got himself killed.
On the other side of the coin, some people either see Private Lawrence as The Woobie who was ultimately broken due to being relentlessly bullied by the Drill Sergeant Nasty, while others look at him as someone who really did not have the mental fortitude to make it as a Marine and who really should have dropped out for the good of both himself and everyone else.
Or, it's Joker who is unfit, since he does nothing when he finds Pyle loading a rifle in the head (a violation of at least three regulations). Instead of either taking the (unloaded) rifle away and alerting the MPs, or just alerting the MPs, he just stands and watches Pyle, who has clearly snapped, load a magazine and load his rifle, and as a result two Marines die.
Crosses the Line Twice: Hartman's insults are meant to belittle and demean, but one could sympathize with Pvt. Pyle's giggling due to the sheer creativeness of Hartman's ranting. Truth in Television, many Boot Camp instructors are purposefully funny, they try to teach recruits to have the mental control not to laugh, which gives mental fortitude in other areas.
Plenty of actual Navy, Army, and Marine personnel that he's met seem to actually love Hartman... when he's meant to be completely unlikeable, even to the military. (That may be the point, however.)
Almost every YouTube video of Hartman will have some comment along the lines of "My 'Nam drill instructor was just like this, and what he taught saved my life." Whilst not completely implausible, it seems hard to escape the conclusion that a lot of these comments are Phony VeteranYouTube War Experts trying to idolize Hartman and pointing to fictional stories from "the 'Nam" to justify it.
In-universe, Hartman gloats about the Marine-taught shooting prowess of Austin sniper Charles Whitman and Lee Harvey Oswald. Doubly obnoxious because Whitman's massacre would have been barely a year old by the time the movie was set. Plus, Oswald actually demonstrates piss-poor marskmanship, with one missed shot, one neck shot and one off-centre headshot when, with a 4x scope at 88 yards, Kennedy's head would have taken up the entire scope.
Hartman is being as hard on the recruits as he's allowed to be, and that's much more forgiving than combat in Vietnam was. The second half of the movie adequately demonstrates this. the misaimed fandom for this movie is anyone who thinks its either pro- or anti-war; it's just an exploration of war as a phenomenon. Hartman is a part of that phenomenon.
Moral Event Horizon: The Door Gunner crosses it in seconds as he's introduced killing unarmed civilians, gleefully. He then boasts about his "prowess" and then casually jokes with a technicism when asked how he can kill women and children (and 50 water buffaloes too, all them certified). Ain't war hell?
Pvt. Pyle's suicide. The blood (and pieces of brain) splattering on the wall behind him doesn't make it any better.
Pvt. Pyle's treatment by Gunny Hartman and the other privates in general. As well as his breakdown.
"Shoot... me... shoot... me...". Not to mention Joker's thousand-yard stare after the deed is done.
The Mass Grave, especially the fucking creepy music and the bodies. The white powder on their face...shudders.
When Crazy Earl wants Rafterman to take a photo of him posing with the corpse of a dead NVA soldier.
One-Scene Wonder: The Da Nang prostitute ("Me love you long time"), and the door gunner who shoots Vietnamese civilians from a helicopter ("Get some, get some!)"
Squick: Pvt. Pyle's suicide. See High Octane Nightmare above for more details.
Unfortunate Implications: The Vietnamese hooker who (in)famously says "Me love you long time", another hooker and her pimp in a later scene are the only Vietnamese characters with any dialogue in the film.
In the 1960s it was acceptable for Drill Sergeants to strike recruits, but no longer.
Same goes for the infamous "This is my rifle, this is my gun. This is for fighting, this is for fun."
Also applies to the "Eskimo pussy is mighty cold" cadence that the recruits chant while running. In general, this was a lot more common before women were integrated into the US military in the 1970's. The military was allowed to get away with chanting cadences that had more sexual references or sex related humor in them.
There's also the way Black marines were treated and the usage of the N-word.
Weird Al Effect: Mention the name, "Gomer Pyle" to someone. A younger person will probably think of "the fat Marine recruit from Full Metal Jacket who blows his brains out" instead of "the gas station worker from The Andy Griffith Show who got a spin off sitcom where he was in the Marines" (Which is where the name came from and why Gunny Hartman gives it to him).