Every so often we get somebody who's pure transmit and demands that everyone adopt their particular crusade. Yours is cats. I get it. But you can't pigeonhole and insult people simply because they don't rush out to sign on to your crusade. I just don't share your sense of alarm. I've been charged and I've had to defend my kill and myself a hundred miles from civilization. I've been rocketed in Afghanistan. I just can't feel threatened by a housecat. If you think I'm an armchair hunter because I'm on this forum, so be it. But I can sit in my armchair and admire some nice taxidermy on my walls.
I understand your thought that you feel justified to shoot cats under the "threat to life or health" argument. But good luck with that one in a court of law. I've lived all over the country, to include a lot of time in Alaska, which has some of the most liberal "defense of life or property" laws in the country. Your argument on this matter is like shooting wolves because they might be carrying rabies. It's akin to ranchers in Montana arguing that they have the right to shoot any buffalo on their property because they might be infected with brucellosis. This isn't a matter of personal values...it's legal definitions. And legal definitions care about things like justification based on actual threats vs potential threats. All folks here are saying is to be sure you're right with the law. And that's not just regarding killing feral cats...it's also regarding raising field mice and releasing them into the environment.
You certainly seem wound pretty tight on the matter, and I've gotta ask...at what point do you move from shooting every cat on your property to a preemptive approach where you start killing every cat you find before it gets to your property, or in the belief that you're bettering society?