It's not even all about bombs. Yes, we know the research is going to bennefit bomb-making, but it's also a national security thing. If we can create a power plant with the immense power potential of fusion, we've effectively made a way to start weaning ourselves off of foreign energy on the fast track. Less dependency on foreign oil means we are not dependent on them. Not dependent means we can use fusion bombs without worrying about our oil supply... OK, so bombs are a pretty big part of it.