Heres the thing these people who are going to harass people over their dps or performance already do so. The only thing that will change is instead of a put down being you suck ass at this game it will be you suck ass at this game for doing low dps or (generic dps number here). I have a paladin in my static who had no idea his damage was super below what it should be because he had 0 feed back from the game its self on what he was doing wrong. I helped him with his rotation showed him a parser and he literally does triple the dps he did before. Parsers aren't going to change how people behave at all it's just a tool.

TLDR: the people who already harass people over dps run parsers now. The only difference will be that people will use a # tacked to their you suck as opposed to their just you suck insult they use now.