>Doesn't it do the opposite though? It gives criminals a map of exactly who they shouldn't rob, lest they risk getting shot. I imagine criminals will go after the softest, easiest targets, not the hardened, well-armed ones.

I'd say thieves generally want to rob when _nobody_ is home so it doesn't matter if they are armed or not. Knowing that there are guns stored in the house is just advertising something specific they might be able to steal.