Thats the same way the MPAA is. Movie A has an artistic, well made sex scene showing minimal skin (front and back but no porn contact. Movie B has knives, bombs, guns, and blood. As well as a bunch of deaths. Movie A is rated R and Movie B is rated PG-13. That has never made sense to me.
It's truly insane what the American culture teaches its youth; sex is bad, but death is good.