Everywhere in the world, owning a dog is on record as being the single most effective deterrent to robbery or home invasion. Even in my army days in Iraq, armed to the teeth, we would think twice before approaching a house with dogs.
I just didn't bring it up before because if they don't already have a dog they're probably not interested in getting one regardless of the situation, for whatever reason.
That and I've lost more trees since I getting my new dog last month than I have in the previous two years. They experience a certain learning curve with bonsai as well, it turns out.