I had a tank try to vote- kick me for tanking (on my Vanguard), when I had been assigned DPS although I had queued as tank-only. She wasn't using taunts and had chosen to guard me (though I had more health and armor than her), so I guarded the healer (who never actually healed me, as I kept popping armor buffs, etc.), and aggroed one of the four bosses fighting us (in Mando Raiders). So, she called me a troll and attention whore, then tried to get me kicked, and then told the healer not to heal me during the final battle when I aggroed the boss. After the run, I got this homily that was TL;DR, "Go f*ck yourself and l2p DPS, you troll."
Group finder is so much fun.