I'm a Diaz fan, but the UFC spends 10's of thousands of dollars promoting a fight and when one of those fighters their promoting refuses to show up to promotional events, what other choice does the promotion company have but to do something about it.
Diaz has always been a do it my way kind of guy and I've liked that about him, but like Dana White said years ago, Nick just needs to "play the game" just a little at least. He doesn't need to go to these conferences and be the most charismatic guy, just show up and answer questions however he wants t answer them, but be there by all means.