I think several people just hate him as a face. I know I do, not that he isn't good at playing a rebellious, anti-establishment kind of face (he's no Austin, of course, but who is), but he's much better at playing an asshole and/or a "I think I'm better than you" kind of individual, probably because it's closer to his real-life personality. But their hand was kind of forced considering he was getting mega face reactions as a heel, including having his name chanted in equal part alongside The Rock and Undertaker's.
Also, as mentioned,a good chunk of the IWC just have some innate part in them to hate someone or something that gets popular, even if it's someone or something they like. Hell, people clamored for years to see CM Punk get pushed, and yet when he finally received a push in 2011/2012, several of those same people shit all over him as a boring champion and an overrated wrestler. Not saying there isn't validity to their opinions, but the IWC has always had a habit of behaving this way. Many are doing it with Daniel Bryan as well. Wouldn't be surprised to see it happen with Dolph Ziggler too, in the event that he got a huge push to a top spot.