Not sucking on the player's genitalia for collecting your daily ration of bear asses is OK, even great. Being a twat for literally no reason at all (hey, we have saved the world several times by now, aside from the fact that we are elite soldiers of your beloved banshee, you idiot)... Not so much.
Taran Zhu in MoP was pretty similar, but at least 1) he acted on his own, not as Sylvanas' #1 bootlicker and 2) he had no reason to know who we were, all he saw were invaders whom he probably didn't like (which made sense), but had to be dealt with anyway.