I get everything that you are saying. I can even appreciate how he might feel about the situation and I think it speaks highly of him that he wants to honor his original commitment. It comes down to the decision of how you are going to respond to schools sending you letters after you have already committed.

He chose to laugh with his family at the idea that he might actually go to Utah and then share that with the press

I don't think he's a bad kid because of this. It may have been a little more mature of him to see the letter as a sign of respect from the University and then kindly let them know that he is going to honor his original commitment. The laughing bit just sounded a bit condescending to me.