This is probably not surprising to anyone living in the U.S.
The film media has been cranking out ultra-violent content to such an extreme that any retail videogame would pale in comparison (i.e. Saw vs Man Hunt). Several music genres glorify violence in their lyrics, music videos, and concerts.
But looking at those statistics, calling sexual content more offensive is probably a stretch. If there is something Americans love other than violence, it would be sexual content. Similar to violent content, movies and music has always glorified sex in American pop culture.
I believe the reason why parents allow more violent content over sexual content is due to its availability of mimicry. Kids find violence fascinating and over the top, something that doesn't feel intimately real but more resembling cartoon violence. Sexual content is more easily mimicked especially if there is any in-game interaction involved. Though some cultures have an openness to sexuality, I think American culture has a stronger duality to this aspect than violence.
What is really sad is that they find Gay kissing offensive at a similar level as a severed head. I doubt that heterosexual kissing would be found as offensive to these same people. I don't believe they would think that kids would mimic such behavior. I think they are personally offended by the action more than anything.
How does this affect a gamer?
I would rather like people to be offended by sex than violence. This is due to the fact that games are more fun with violence, but sexual content isn't necessary (at least for me).
-And yeah, sorry I got no funny pictures for you people. Just look up at the two girls punching each other an let it go-