I have a question. I posted a video of Ravi…

I have a question. I posted a video of Ravi Zacharias (which I can post in comments) and had a discussion with my atheist brother. His position is that objective moral values do not exist because they not only change but also because we can choose them, making them subjective. I appealed to moral duties and his response was that society can determine morality with Laws. My response is that if morality is only group ethics and then we must constantly change what believe is ‘right’ based on the societal norms. Likewise noble and heroic people who defied their governments for good causes were wrong because they ought to have complied and adopted the new wave of moral standards. Comrade Mao, Stalin, Pol Pot etc were just ahead of their time then according to that view.

How do you respond because I can’t get through.