Typically, when people criticize the Diaz brothers they operate in a fantasy world where everyone should be held to the exact same standards.
Nate and Nick don't apply to the rules to which most MMA fighters are held. Why? Because they've fuckin earned it, and aside from their elite skills, their unique outlook is the reason they are so beloved.
They owe the fans nothing. They've given their lives and brain cells for our entertainment (even if our entertainment isn't their ultimate goal), and they fight in a way that protects neither of those things they've given. The UFC did try to bury Nate Diaz. They also underpaid Nate Diaz, probably because Dana didn't understand the appeal because he applies his own biases to what he thinks the fans want, and he wanted to bury guys that he knew he couldn't control. That's why Dana and the Diaz brothers have clashed- Dana loves people who are company men and who accept the assessment that the UFC makes of them. The Diaz brothers realize their worth, and see that the UFC wants to downplay their worth, so they go out and set their own bar. They want to dictate how important and skilled they are, and they don't give a shit about what the UFC thinks. It's worked pretty well, too. If they don't want to fight, nobody can be mad at them. If they want to fight, we should welcome them with open arms and hope Mr. Thumbhead has to relent and make them filthy rich.