In my opinion a lot rock music is much more meaningful the much of the mainstream stuff. Now I don't mean to say all mainstream stuff has no meaning or value to it, I like both that and rock, but it's just my opinion and analysis.
I don't think rock music will influence young people in a bad way as such, and to be honest R&B and Hip Hop are more likely to influence people in such a way. But it's each to their own and people should be allowed to listen to what they want without restrictions such as different influences :)
The day that never comes is a great song about a real problem in the world (one of the posts below mentions it), One by Metallica is also a great song and possibly one of my favourite songs.