You bring up a valid point. As tenacious a defender as Artest he, he is just as brutal at taking offensive opportunities away from teammates. At times, he's just as likely to get into his own personal mano-y-mano offensive battles with the opposition's top scorer - and will not back down.
I remember reading a blurb last season that Artest constantly frustrated his teammates because he often "broke off" plays that were signaled in from the sideline. He did so that he could command the ball in the post, while looking for his own opportunities.