I think part of the problem is that often people who play tanks and healers (not counting the ones that only do it for fast queues and/or ego boosting) play the job because they like to help/protect others. When these 'others' are aggressively mean, then sometimes the more helpful but less aggressive tank becomes more withdrawn and then suddenly will never tank PUGs/DF/PF groups anymore and only tank for friends/FC. I'm a case in point - I got tired of all the hate/rage in DF even doing roulette, and even though I want to help out by lessening the wait for dps, I now almost exclusively only use my bard for anything public and only tank for friends... Just a thought from one of those tanks that are quiet when people rail against me but then eventually just leave and don't public tank anymore :/
Its sad really, people complain not enough tanks and they have to wait along time in DF, then when the tank is not up to their standards they ridicule the tank and are verbally aggressive too. Its a no win situation, I just ignore those people quit group and take the penalty, no big deal.

If its on the same server blacklist them. If the players are respectful to you and each other and understanding which is rare from what I see and hear, then great, you had a nice group and your game time just got a little better