The Rock gets hate because people genuinely dislike that he's "too good" for the product. It's like being on a crappy basketball team that loses all of its games. Then one day an awesome basketball player joins your team and you guys win EVERY game, get to the playoffs, and become champions. Throughout this journey, the awesome player gets all of the credit, glory, and cheers. Meanwhile, you and the rest of your buddies are an afterthought. The fans who have been watching this PG Era product for the past 8 years or so, see The Rock as that highly-praised jock. They mostly feel they can relate to the shade that CM Punk and Cena threw at The Rock because he wasn't a part of their "struggling" era.
I'll admit that the 1998-2001 version of The Rock is easily my favorite wrestling gimmick/talent of all time but the way he turned his back on the business (and us fans), was not the best way to handle it. He made sporadic video appearances twice and showed up to a HoF ceremony for his dad but that's about it. He doesn't owe anyone anything. Especially since HE got himself as over as he did through rigorous in-ring training, speech classes, character acting, creativity, and countless hours of exercise. But on the flip side, none of these fans booing him owe him anything either. It's their right to feel dissed or to feel that he isn't worthy. I don't agree with them but being able to think or feel what we do is what makes us who we are. So accept it and move on.
It's lonely at the top. You can't make everyone happy all of the time. Take Justin Bieber for instance. Everyone hated the kid even BEFORE he became a criminal nuisance. They complained that his music sucking was the reason why. Yet most of them don't even like pop music in general. You know the same people who don't listen to One Direction, Rhianna, Katy Perry, Kesha, Gaga, and all that jazz. We complain. "THAT'S WHAT WE DO!!!!", said Father Henry.