Nothing.
How much I enjoy things, defines their quality. Therefore if I enjoy something, it can't be low quality and I have nothing to feel guilty about.
If I enjoy a girly J-pop song, then that must be a damn catchy song. If I enjoy a cripple porn game made by 4-chan members, that must be a pretty high quality cripple porn game with emotional depth and quality writing. If I enjoy a cartoon about ponies saving the world with the power of friendship, that must be because that cartoon is actually funnier than the rest of the others around it.
The whole "guilty plasure" bs is just an excuse for people to act like they are oh so sophisticated and tasteful that they wouldn't GENUINELY enjoy certain things (even when they evidently do), to circumvent the fact that they don't dare to call out the majority's Sacred Cows, their belief that you are simply NOT SUUPPOSED TO consider certain things good, not even if they are.