I am sorry but don't act like a tool when you are the visitor. No he probably didn't deserve what he got but If it's me, I am walking around with my head on swivel and minding my own business.
From a video I saw he was holding up a sign and running his mouth.
Nothing that deserved being kicked out or assaulted by Security.
I personally hate going to games because everyone feels they are the 12th man and the screaming helps the team, but that doesn't excuse bad decisions by employees either. A rear naked choke is a potentially deadly maneuver.