What would have happened to Barnett if he had shoved the ref to the ground as a reflex action, thinking that he was being grabbed by an opposing player?
There is no reason for a ref to grab a player around the neck from behind, even if he was breaking up an altercation. If anything else, it puts the ref in jeopardy.
All of the other officials don't seem to have a problem separating unruly players without resorting to that extreme.