I feel the same way. I was in a MM and the tank just decided we were doing the bonus boss. Didn't ask, didn't apologize, didnt give anyone time to prep, didn't go over tactics...just facepulled. Then he copped an attitude because the whole group was upset. Told us to "deal with it" so I just left. Of course he starts spamming nasty pms my way so I put him on ignore.