I see your point that ingroupism itself is irrational and counter-intuitive to altruism. But lets take this a bit further - what forms the basis of human relationships? Randomness rules this world and your relationships are a clear example of that - they are driven by chance. To say that bonds based on arbitrary markers is irrational is to deny us of our humanity, deny us of reality.
Human instincts don't arise from randomness however, they are designed by evolution. Therefore I think the answer in altruism doesn't rely on negating humanity but rather balancing it with our conscious free will. This requires recognition and understanding and is not easy.
I see your point that ingroupism itself is irrational and counter-intuitive to altruism. But lets take this a bit further - what forms the basis of human relationships? Randomness rules this world and your relationships are a clear example of that - they are driven by chance. To say that bonds based on arbitrary markers is irrational is to deny us of our humanity, deny us of reality.
Human instincts don't arise from randomness however, they are designed by evolution. Therefore I think the answer in altruism doesn't rely on negating humanity but rather balancing it with our conscious free will. This requires recognition and understanding and is not easy.