I don't think it's right to make kids think violence is good, I don't think it's right to make kids think sex is bad.
Kids having sex most certainly is bad, having a child when your not financially stable is a horrible thing to do to the child, so inferring that sex is bad to kids is a good thing, by the time they are able to take on the responsibilities they will know it is not a bad thing.
We should inform kids about sex instead of telling them it's bad. We should let them know what could happen and what they should do to protect themselves.