To be fair, Sean didn't try to use the underage thing to get out of his contract with Cobra. Everyone involved admits that Sean was 18 when he entered into the deal that got him the car in exchange for shooting a bunch more scenes, only one of which he ever did.

In short, Sean has shown himself to be an extremely manipulative kid, but Bryan also, according to the reports of Chad and others, did unethical and illegal stuff.

I'm not saying that Bryan didn't have good qualities, I'm sure he did. But Sean certainly had some problems with the way he handled things.