I think you may be a bit too influenced by how the US works.
Over in Australia, violence really isn't a problem in the majority of places IMO.  I run around random streets at night and never fear anyone beating me up or similar.
And a lot of our movies/games come from the US, so wee get exposed to the same violence etc.

I personally don't think it's necessarily bad to tell kids about sex.  You just need to explain to them what they should and shouldn't do about it.  In fact, kids probably know a lot more than their parents may think they do, so it might be better to hear advice from an informed adult rather than rely on rumours spread amongst friends.

It's just that sex is treated as such a taboo subject...