Except not. Howard and Kidd were between Artest and Yao. Artest tried to go between them. When they see Artest they stiffen up and Howard pushes Artest's hand away. Artest didn't shove or push him. He put his hand on him sure, he was in the way, but not in a volatile manner. He did not give him a "slight push". I would agree that I would rather Artest just stay away from situations like that even though he didn't do anything wrong.
It was the way Artest ran over there all hurriedly that made it look like he was trying to mix things up. And Artest's always stoic expression you can't really "read" his emotion or guage his intention. Definite reputation thing. If it was Barry or Hayes doubt they call anything. I think Artest was trying to show that he's part of whats going on with this team, which he gets respect for. He did exactly what he needed to do, just had to get the first one out way.