since when is leaving your cat free irresponsible? everyone who doesn't fear a car will run over it or lives in rural areas does that.
I've had outdoor cats for years and I've never smelled their piss. It's also plenty of cats where I live now, no smell of piss either.
It's always those damn martens that like to shit in front of your door and piss on the car. Cats don't do that.
I find much more irresponsible the people who let their dog shit all over the sidewalk and don't clean up just because there's no police around.
Anyway I think the motion detecting sprinkler is a good idea.
Not only is it against the law, but all pet owners are responsible for anything their animal does. Cat scratches my child? The owner is responsible. Cat pisses on something and kills it? Owner is responsible. Cat gets into a fight with another pet in its own yard and hurts it? On the owner.
I don't have any desire to harm the cat just that the owners keep it in their yard unless leashed. Never would I allow a pet of mine to run free in the neighborhood, dog or cat.
And you're right, I find people who walk their dogs and don't clean up after it equally detestable, if not more. They're actually witnessing their dog shit on someone else's yard and willfully choose to leave it.