I have found raid groups will generally be forgiving a raid leader that is an ass, if he/she knows the classes and boss strat very well. That said, even that lasts only so long before the stress of both the encounter and the yelling get to people.
I work with a guild that's pretty chill. My only constructive criticism of the group, is more need to speak up when they screw up so we can fix it and move on. but....I would guess that comes from years of being bit at when speaking up.
Reading these posts, I would be curious how many quit not due to the dynamics of the boss, or the cycle of progression each tier, but how they were treated in guild raiding.