Why do people hate John Cena while they love CM Punk?
It is a common story of the defender of the status quo and the troublemaker who wants to shake it up.
Fans connect more with CM Punk's story than John Cena's. Cena was originally this freelance wrestler who rose through the ranks by assuming the status quo as an underdog, eventually winning the biggest award in the industry, the WWE Championship. He then he kept winning and losing the belt over and over again. This went on for more than a decade, and as talents came and went from the company, Cena's reign increased while his reputation fell with older fans. Children love it. His merchandise sells millions. John Cena is the face of WWE.
CM Punk was the face of the fans.
Punk had always projected this arrogance that he was better than you and me in the ring and he wasn't afraid to say what he had in mind about the industry. It was a tie in all areas, but it was not going to be corporate. Punk was never going to be "the man," but he followed his narrative. And Punk's narrative turned him into an outsider who sees the hypocrisy of the company he's in.
A company that has an anti-bullying campaign still celebrates the bullying tactics of its figures, heels, and especially John Cena. A company that would rather have a hulking beast with no fighting skills than a smaller technical fighter that could deal with the best of them. A company built on a wrestling legacy, although he rarely says the word "wrestling" and refuses to call his wrestlers "wrestlers", but rather "superstars" and "divas." A company whose greatest appeal and source of money is always portrayed as a loser despite the fact that he is (at the time of this writing) 15 times world champion.
Punk represents fans who are smart enough to look behind the curtain of professional wrestling and pay attention to what goes on off camera while Cena is corporate, an incarnation of "the man" posing as a people's voice. Fans feel that Punk was harassed outside of the company and they feel that a similar wrestler, Daniel Bryan, has been canceled by the company because he doesn't fit the mold of what WWE wants. This is why fans hate Cena while they remain fans of CM Punk.