“Because we depend on society for our survival.”
The importance of survival implies an inherent value to life which there is no reason for besides the idea that there is a higher meaning to life. If there was no deity behind life we’d hold no more significance than any other matter and I think most people would agree certain matters don’t hold intrinsic value. For an example gaseous waste. Now once again atheists would typically argue through evolution for a meaning to life but it’s a very unsound argument. Evolution can only point to a purpose, but not a meaningful purpose. I enjoy boxing the PURPOSE behind contracting my muscles in a way that leads to my glove making contact with their face is to hit them and inflict pain, but the vast majority of the time I have no personal conflict with this person therefore having no meaning behind it. Now if I was walking and someone harasses or attacks someone and I punch the assailant to fulfill my God given mission to assist and love my neighbor that is meaningful.
“Then morality is subjective, not objective”
No, you just failed to use your brain. If the primary moral is to fulfill God’s commandments then following a commandment from God is the ultimate moral act. Something can be objective while having variables an example being a cars maximum speed although its minimum speed is 0 and it’s maximum is let’s say 150 mph it can still go anywhere in between those speeds.
“I am the LORD your God. You shall worship the Lord your God and Him only shall you serve.“
is the first commandment which puts it above ‘thou shalt not kill’ and therefore it holds more importance than the latter. Another argument is that if we are to believe in free will then if God tells us to kill someone He is working through us and we are not doing it out of our own free will. We are following God’s command out of our free will, but the actions we perform are through His will. Further you’re pro-choice so you clearly see no wrong in subjection involved in morals. Really you believe in subjective reality, a human is what you believe to be a human rather than what is genetically a human, a woman is what ever you believe to be a woman, a man is whatever you believe to be a man, etc.
Now an easy objection to this would be that I support capital punishment which is true, but I don’t believe it to be morally just. Objectively if I vote and support a state official who believes in capital punishment inherently I aid in the use of it