I encountered such a person when levelling my healer. Someone in the group started going off on him about how that's not how lfg works ect.
Eventually the douche begrudging starts tanking (by tanking I mean pulling mobs and standing there while dps do all the work), I heal everyone else exept for him, when he starts going "Omg nub healer, where were the heals?!" I said "I just queued as healer for instant group.". He left after about five minutes.