We cannot impose our own cultural morals on others just because we don't share those morals any more than we can force our religion on others just because we don't share their religion. We may not like it, but it's frankly none of our business. We may think our beliefs are the right ones, but I can guarantee that others disagree, and think their beliefs are the right ones.
I agree that a culture of pedophilia is revolting to me... but there are a lot more revolting things about Afghan culture, such as their dispicable treatment of women, that bother me more. Sadly, we can't change the way they treat their women, either. Only they can do that, and only through the evolution and maturity of their culture as it has more contact with societies outside of its own. Since we're talking about a tribal nation, that's not gonna be happening any time soon.
I disagree, I think that we should impose our belief on them and that we have been doing it. Are there not many movements for the emancipation for women in the area? Sometimes the only way that culture evolves is through conquest. It worked for the world before, we just need to jump start their evolution.