didnt Kobe elbow Arrtest? Arrtest doesnt outwiegh him by 30-40 pounds?  however im just going by the letter of the law, i didnt see the elbow play or the replay. and a weight difference shouldnt matter at all. 
He elbowed Artest to the extent he was trying to get position.  That happens under the basket all the time.  I watched it live and have seen several replays.  It wasn't anything like the Howard elbow.  The refs actually called a foul on Artest on the play.  Artest then ran all over the court and got in Kobe's face crying.  Artest is a tough player, but he acted like a sissy on that play.    
Artest is actually about 50 or more pounds heavier than Kobe.  He's about 260.  Kobe is a little over 200. 
I think the weight difference matters, because it takes a lot more effort for a small player to fight for position with a larger player.  Size difference also plays a huge rule when it comes to calling flagrant fouls.