I don't think people advocating for a parser want to use it to abuse others or shun them, I'd hope. Personally, if I'm on NIN or BRD, I LOVE knowing my numbers so ask for them so I can compare myself to others and find out if I am pulling my weight and how i can get better. I found out I was a lil low on NIN, and that prompted me to look at how I play and change some things in my rotation to get up to par with where I thought I should be. On WHM, I can tell without a parser, really when a dps is doing low, and even account for them having to avoid AoE (melee) or sing (bard). It is especially obvious if they request huge pulls but those pulls take 2/3 of my MP due to how long they take to down.
I think a parser is a tool people would use to better themselves, even though a few mean ones would abuse it to call out bad dps. Also, I'll add that I don't think parsers even really have a place in content you're doing with PUGs, and therefore, like someone said maybe should only be given for pre-made groups. If you're with pugs, there should be no expectation of optimal performance, I'd think, rather just casual clears ^^