What separates a human from an animal is our ability to think into the future and make proactive choices instead of just reactive responses to stimuli.

TBH, I'm not personally sure that people are innately born with that ability, or at the very least I believe you can very much dissolve a person's ability to do this. I don't know as though anybody that got captured here is an example of such a person, but I do think it exists.

If they really have no control over their actions then they were dangerous animals that were a threat to human kind and and the world at large. Their death is no worse than shooting a rabid dog in fact it is a net benefit to the world.

I don't know that a dog becoming rabid & then having to be put down is a net benefit to the world. I imagine that's a net increase in suffering within the world overall, tbh.

If they were just doing what their nature and culture dictated then nobody has free will and nothing matters and I’m not responsible for calling you a fucking moron because I was just programmed to say it by my preordained interactions.

I mean yea; that could very well be. :shrug-outta-hecks:

(Though I might contest that a lack of genuine free will in people means that "nothing matters". It just means you can't attribute a definite & essential moral character to any particular person; nor can you extract it from their actions, or beliefs. It means that anybody could conceivably become a fascist, under the right circumstances, and that you should seek to eliminate the possibility of those circumstances where & when you can; not that it isn't a bad thing if someone is one.)