There are so many things wrong with that analogy; I don't know where to begin.
First of all, has your neighbor shot other neighbors or thrown grenades at you or your neighbors? If so, he has been warned by the police and the police may have arrested him and put him in jail. If he didn't go to jail, he's on probation in which he's not allowed to own or possess any of these weapons. That's part of his probation agreement. The police may check on this, but if they feel he is hiding weapons, they will do a full search. Now if they still have conclusive evidence that he still has these weapons, he will be arrested and prosecuted.

Sadam is a threat, not only to his neighbors, but the whole world. He's proven he can't handle the power of having "big toys" and playing nice. He wants revenge on the US because we are a primary UN power. If something major happens in the world, we are the big brother that has to slap the wrist and tell them that's wrong. This is only done when needed to prevent things like Hitler. He started with overtaking one country and slowly worked his way across Europe. What would have happened if we would have entered WW2 earlier and prevented him from doing this? More importantly, what would have happened if we didn't enter WW2 at all?? Sadam has shown similarities to Hitler. Instead of waiting, we are taking care of the problem now.