There is one thing that just about anyone that has ever played an organized sport has wanted to do at one time or another--hit a ref. Those guys are annoying. To be fair, they are charged with a pretty tough task in regulating the game. More often than not they do just fine, but when they do mess up boy do they mess up.
So when Carlos Boozer made a heck of a play and in his excitement turned while pumping a fist and inadvertently nailed the ref people probably laughed first and hoped he was okay second (cause it looks like Boozer got him pretty good).