That means he's a failure as a heel. What kind of a heel that gets cheered. You think all Cena haters hate him because he's a face, no because he sucks in many ways, and others hate him because of his character, so don't think he will have them all. I will always hate him because of the fact he's over pushed and gets way to much credit for everything.
Taker got cheers even when he did the whole ministry thing. He was clearly heel and although he got some boos from (say) the casket match with the Rock, people still generally loved him. Now don't get me wrong I don't intend to even compare Cena to the Undertaker, but I just mean to give an example on how the crowd will even cheer on a heel.
As for everything else that you said, I don't necessarily hate Cena. Hate is pretty strong for me to use, but I also do not like Cena all that much. I think it would be interesting for Cena to make a turn to Heel for a while like Hogan did with the NWO. Hogan's abrupt change to a villain devastated his fans, but it was further character development. Like I said before I think Cena WANTS to change things up, but outside politics play into it in more ways than one. Cena is the face of the WWE whether we like it or not as long as the kids love him and it will also reflect positively on Linda McMahon's part in Senate.
"Those boos from older fans don't bother WWE very much. The company is more than prepared for those boos each and every week. These aren't like the times of Rocky Maivia hearing "Die Rocky Die." These are just a bunch of adults that are angry at the children they sit next to.
Those kids are another reason that things will not change. The WWE wasn't changing back in the day when the action was catered to the kiddies and things were TV-PG.
Those children are the ones who insist on coming to WWE live events. They are the ones who will buy anything with John Cena's face on it. Cena is an icon to them, just as Hulk Hogan was an icon to many of the older fans."
-Some article on google
(Apparently my post count isn't high enough to post links)