Well, I _liked_ Thin Red Line. I thought it was beautifully filmed, and I didn't see too many firearms screwups in it... The looks at the characters really said things... the passed-over officer, the youthful fast-track general, etc... I actually thought that Penn did a good job. He's an actor, and a pretty decent one. Not a great human being, but a decent actor. Don't have to like him, you know?
And yeah, it'd be possible for a pineapple grenade to do that sorta thing. The human psyche is a funny thing.
TRL isn't a war movie, but it's about war, and about what it does to people. When the puzzled, almost conscientious objector, protagonist sacrifices himself so that his buddies can get away...
EATG also struck me as a decent movie. IMHO, better than _either_ of the sniper flicks as far as the actual shooting.