Don't you want your kids to see you as a role model and follow your example? Or do you let your kids decide for themselves wether they can drink alcohol or not? Or if they can eat then whole bars of chocolate at once? Yes, there is evidence that drinking alcohol and eating too much chocolate is unhealthy, but when it comes to atheism vs. religion there is no proof that one is better than the other, it is all personal opinion.

Furthermore, I even think banning nudity and violence from the media wouldn't make Ender happy, since people are still wanting these things. In my understanding, he wants people to realize themselves that these things are not appropriate and no ban would lead to this realization.