Of all the things I've heard said about GWB, timid responses were not among them. I doubt anyone considered him overly cautious. He certainly believed in American military adventurism.

However, the basis of Obama's foreign policy seems to be that if it doesn't directly affect American interests, or American citizens, he really doesn't want to interfere too much. These people are essentially forcing him to address people getting murdered specifically because they are American. They are making it his business.