I do believe some of the things he says are true. Rampage doesn't really have a lot of reasons to bash a company that has never pushed him away and given him millions.
I also believe the UFC could have dropped him like a hot potato after he went on his "rampage":
He led pursuing officers on a chase while driving on the wrong side of the street and on city sidewalks in his lifted Ford F-350 with his picture painted on the side. During the chase one of the tires blew out on his truck and he continued to flee while driving on his rims.
That was some pretty messed up stuff. Someone could have been killed. Normal people don't do that kind stuff. That's why I take all his whining and complaining with a pinch of salt.
To quote Rampage himself loosely: "that boys cheese dun fell off his cracker".