On human worth

A reddit user has posed the following questions and a disclosure about himself. His questions are indented

1) Where do you, personally, derive the feeling from that (human) life has any value? Is this even a valid question, or do you simply accept the feeling as an evolutionary instinct of sorts?

There is only one source, I value my life and I would expect others value theirs. Beyond this, I think the universe is indifferent to how I feel about my life. It is possible to argue that human life has no value to military strategists except as pawns or to ISIS except as a means to an end.

2) What would you say is the reason that atheists should condemn current and historical crimes against humanity, like genocide, colonialism or slavery, in case of the absence of any downsides for the side that commits those crimes?

Because they are human beings. The second portion of this question makes no sense.

2a) Context: All atheists I have ever spoken to do condemn these crimes, but were unable to explain to me why they did. “Because no human being should do that to another one”, or even the categorical imperative, do not really seem to apply when purely logically, there is no problem with the “strong” eliminating the “weak”. What am I missing?

It must be the case that you wanted an answer that maybe be transcendent that is why you find their answers inadequate.

Disclosure: I am a Catholic from Europe – not that it matters, but I guess the question would arise anyway. No, this isn’t flamebait, I am genuinely interested in understanding where some of “you” atheists are coming from. I tried to formulate my questions as clearly and respectfully as I could – if I failed, please excuse, I am not a native speaker, so I might be pressing buttons I don’t even realize are there.

Here we had a discussion on the same