Drone strikes. Obviously, President Obama doesn't want to say anything bad about the gobs of strikes he's authorized. Neither does Mitt Romney; if you're going to spend your whole campaign calling Obama a hyper-apologetic girly boy, you can't turn around and complain that he kills too many people! But American drone strikes--which seem to always target Muslim countries, and sometimes kill civilians--are famously unpopular in the Muslim world.
On this issue, Muslims have a very good reason to be angry. I'm not looking forward to the "foreign policy" debate next week. I think the candidates are very similar (and fairly dreadful) on foreign policy.