Why are low standards for dps acceptable?

[DPZ2]

Because believe it or not, most content in this game is pretty easy and could be done in your sleep if everyone puts the effort into learning how their job is played. The only content that requires any amount of attention is Savage

Yeah -- so why are so many people treating a 'post 60 level dungeon instance' that doesn't appear to provide any useful gear on the way to iLvl 170 as if it was end-game content that had to be played at Savage DPS levels?

More to the point, why do those people think that insulting everyone else in the group because they aren't responding to Party Chat is ok?