"A" hit may not have been avoidable. "That" one was.

Re-watch it if you can. Desman Stephens is coming from a slight angle. He is in a forward lean to make the hit from a couple of yards away as Moore is leaned back to slide (which is, of course, a split second - agreed there). There was time for him complete the natural action of letting his momentum continue forward and either graze him or make contact with his upper torso.

Instead, he lowers his right elbow directly into the helmet. It was cheap and dirty. And the stupidity could have been forgiven had what transpired in the time afterwards not taken place. He was contrite only with the consequences of it all breathing down his neck a day later.