Why are low standards for dps acceptable?

[DPZ2]

However, [you] need to accept the consequences of such a choice. This is a cooperative multiplayer game. If you make choices that deliberately make it harder for the rest of your team, they have every right to be mad about it.

From what I can tell, the original post was not about deliberately making it harder for the rest of the team, it was about <WARNING: extremely loose interpretation follows> "I noticed X and was fairly inept at my attempt to correct the problem because I was frustrated that the person wasn't giving it 100% like I require". [Being generous here, as the OP knew what he was saying ... and that has consequences as well].

Unless you are certain that another person in your group is deliberately messing around (not just sub-optimal according to your standards), you can be upset, you might even provide a few encouraging words. Venting might be therapeutic, but has consequences you may not yourself like.