If you're going to try analogies, make them accurate.
Try the analogy again, only this time include the fact that the neighbor did at one time provably have guns, dynamite, grenades, and mortars. That he used them to kill an number of his neighbors.
That he has killed some of his own children, some buried in the back yard.
Now, he tells you that he isn't going to do anything bad any more.
Harry is looking, but guess what. Harry missed the guns and dynamite the last time around. Harry missed the guns and dynamite in a couple of other houses too. Harry isn't exactly batting 1000.
Now, want to try that again?