I don't quite see where you provided examples before this comment, sorry, could you repeat them? I looked through the thread and see you asserting we don't need religions anymore, but not where you give concrete worked examples of moral questions and how to resolve them with science.

"You can use science to debate if Nagasaki should have been nuked"

I'm not really sure how. It would be interesting to see an attempt. Note that doing this without relying on ambient moral principles like "killing people is bad" is probably impossible but those moral principles don't come from science, as I point out, hence why I don't see how to do it.

"We have laws that prohibit harming others and they don't need religious justification."

Yes I thought you might go there. It doesn't work. Those laws are derived from religious codes originally. Also, the law is not a moral code, the law is supposed to implement moral codes. If you believe morality flows from law as the original source, you have to believe that lawmakers are inherently more morally capable than the people they rule. Moreover you cannot have such a thing as a tyrant because the moment they achieve power and change the law, whatever they do becomes axiomatically moral and therefore they are not a tyrant. Are you really going to argue that? No way are most people going to go anywhere near a claim like that, quite the opposite, it is often argued that lawmakers are less moral than regular people!

"Harming a member of society is against everyones interest because we are part of society and we optimize for a good quality of life of society as that optimizes our own"

This isn't a logical argument from first principles. Harming someone else can very much be in your interest in all sorts of situations. For it to be considered immoral, there must be some higher justification that states that your clear self-interest in harming an enemy is subservient to some other principle.

Claims like "we optimize for a good quality of life of society" don't mean anything concrete. It's just restating a belief that the original position is morally correct in different words. Every tyrant in history has always claimed to be acting for the betterment of society and how can you argue otherwise without some system deeper than "this is morally good because we say it's best for everyone therefore it is"?

That's what I mean by it being difficult. All the obvious answers just lead you in circles.

"Your claim that animals kill each other all the time: killing within their own group is rare. Take two random animals from the same species and put them together in a room and see if they will kill each other."

So by analogy it's OK to kill other races but not your own? That's certainly a moral code that has existed in the past, but it's not one that is accepted today.

But it's an odd argument because it's really common that animals will fight and injure each other within the same species, sometimes fatally. Usually fights over territory or mating dominance. Even in pack animals there are fights over who gets the mates. By coincidence I was at a zoo just two days ago and they had a few cages where there was only a single animal, with an explanation that they had to do this because if they put more than one animal of the same type in the same cage they would fight for dominance. It's normal e.g. the antlers on a deer are for fighting. One of them was a type of crane, and the explanation was that cranes pick a single mate for life and this one had picked "Man", so would fight with any other crane. Animal jealousy!

"You serious claim that the majority just blindly believes in science but wouldn't admit it?"

After what we saw in the last two years! Wow yes, absolutely I seriously claim that. The amount of pseudo-scientific garbage that the population swallowed about COVID is just incredible. Claims that fell apart the moment you read the papers or even just thought about them were routinely passed off and accepted by the population because they came from "experts". It is one of the major themes of our age.