Rather than explaining, have you asked him why this matters to him? Sometimes talking less and asking more helps. If they start trying to explain it, they see that it isn't what they think it is.
Or, if he doesn't talk himself out of it, at least you can get a better idea of what exactly is bugging him and how best to deal with the problem. I think we parents too often project our own interpretations of a situation on our kids, and their thought processes can be VERY different than ours.
(Not that you're doing this. Just that I think it is something to consider. I know I've been bitten by this a time or two...)
The more the child talks, the less likely we are to be wrong about things.
IMHO...
And mad may be a good thing. That means he's not willing to accept that he's less important or whatever because of his age. That's probably a good place to start!
