#7 Doesn't Deserve the Hate: His MMA champion status adds credibility to the squared circle

Like as not, there is still a bit of kayfabe left in professional wrestling.
One of the major components of kayfabe, when it was rigorously practised, was that pro wrestlers had to seem like bonafide tough guys. They need to portray characters and have the physical presence to convince the fans that they could wreak havoc in a physical altercation, even if wrestling is ostensibly 'fake.'
Breaking Vince Russo and Jim Cornette update HERE.
This attitude led to incidents like Meng biting the nose off of a fan who called him a 'fake' wrestler. It also leads to a lot of wrestlers not getting main event opportunities because they don't present a convincing tough guy image.
Brock Lesnar's MMA background makes him a tough guy, no questions asked. His image is good for the WWE and pro wrestling in general, meaning he doesn't deserve the fan's hate.