It's kinda like what that South Park Anime episode parodied. We don't mind some violence, as long as it's not gratuitious, and with the language, they know what's accepted in our house and what it not, but we don't want a bunch of recreational sex in the movies they watch. They don't need to see that at their age.
Oh, come on, gratuitious violence is fun. (kidding)
But you let them watch anime, so you obviously aren't just banning things indiscriminantly!