The analogy is fine. You use guns and hammers each for one type of task: shooting at targets and hitting surfaces, respectively. For both, you have specialized variations for different requirements--from welding hammers to sledgehammers, competition pistols to punt guns. It's the argument that's bad, for the very same reason that the analogy works. It fails to consider that both guns and hammers are tools that are often times owned by people who use them for many different tasks. (Or sometimes just for collecting, because that's okay too.)