Have to agree on the Diaz part more than anything else; he is trying to stay comfortable in front of the cameras and wouldn't take much from the handshake; there really isn't much anger between the 2, not even enough for Diaz to go "gangster".
I'm not a fan of Diaz (although these Primetime episodes are showing different side of him, and show more of why he is the way he is) but I've never seen him truly rocked in the octagon; only going to beat him by decision.