Vitor is probably upset that Chael is getting a title shot coming off a loss while he has a win and isn't getting a title shot.
Sonnen also went after lots of Brazilian fighters when he was trying to get under Anderson's skin, including guys like the Nog brothers, Vitor, Wanderlei, Machida and plenty others. I dont think Vitor forgot about that. You can troll all you want, but sometimes saying "I was just trolling" wont stop a person from wanting to give you a knuckle sandwich.
And of course Vitor isint the only one thinking Sonnen is getting an undeserved Title shot and are upset about it, most people do.