Yes, he was in a vulnerable position, lieing on his back, and had just been in an emotionally upsetting altercation with Wallace. It is perfectly understandable why he would want to give the "what for" to whoever the idiot was that through the beverage at him. In my opinion, Artest was justified. The fan's behavior was monstrous.
through = threw
Right. His ego was bruised because Wallace dissed him on the court and he was too chicken to do anything against Wallace so to uphold his rap-ego he jumped on an innocent fan. The Man!
Funny that he didn't go after Wallace when Wallace tossed an item at him. I guess The Man isn't The Man after all. Just a punk.