I heard this on NPR while driving home. In a news conference today President Bush criticized Senator Obama (not by name though) for his willingness to talk to the leaders of Cuba, Iran, and North Korea. But he's going to visit Chinese president Hu Jintao in August because somehow that is different.
See: Bush takes verbal shots at Obama, Clinton
Yeah, you have to be careful about talking to tyrants as that can be a real career-ender.