Conservatives have a tendency to see military spending as less wasteful and porkish than domestic spending. I suppose that it comes out of a libertarian view of government's responsibility -- the state is supposed to defend you from foreign enemies and uphold property rights, but not to actually help people. And if you see spending that falls outside the narrow obligations of the government as inherently wasteful, domestic spending looks wasteful while military spending doesn't.
That's why it's important that people know about the defense contracting scandals that Josh Marshall has been so intent on publicizing -- first Duke Cunningham and his bribe menu (if you haven't seen it yet, by all means have a look), and now this business with John Doolittle taking bribes through his wife from the one of the same defense contractors who bribed Cunningham. In exchange for bribes, these Republicans would award millions of dollars in contracts for junk that the military didn't actually need. When you trust the party of corruption with national security, that's what you get.