I'm not going to say that people should scoop up kittens under the false pretence of adopting a pet but... BUT if they would end up in the dumpster behind the Humane Society building then I don't see the harm in snakes getting a meal out of it. Not exactly the natural food chain but if the animal is doomed anyway who cares whether it ends up in a burm's belly or a garbage dump? Personally I wouldn't feed any of my snakes stray cats anyway for the very same reason I don't trap rodents to feed them; it's simply not safe for the snakes. Lord knows what diseases and parasites a stray cat may have. I don't have any more of a moral difficulty with feeding cats than rats though.
I feel a little light headed... maybe you should drive...