Why do they restrict movies, but selling mature video games to minors is okay?

I'm 16 and appalled by this ruling. I support that bill, how crazy it seems. Why? Because I do believe that violence and sex in video games and other forms of entertainment is damaging to us! I just have to compare the kids to my school who play them to those who don't to see that, and don't know why anyone else can't see that. Why do they restrict movies, then? Can you please tell me that?