I'm not a mom but the first war in Iraq started when I was around that age. For our social studies homework one night, we had to watch the news, and do a current events project on what we saw.
Personally, kids nowadays are learning a lot more a lot earlier (I see this with my nieces and nephews who range in age from 8-20). I don't think it's inappropriate for a 10 year old to watch the news. You cannot keep kids sheltered forever and they need to start learning about politics at some point.