Here's the essence of the convo.
The conversation was: why is it moral.
Your response: Because the good reaps more hedons than the bad.
My response: Prove it.
Your response: It's to complicated, but I could, just trust me.
I don't let atheists get off the hook when they think saying so makes it so, I can't let you either. Being a Christian isn't a free ride to making poor arguments.
So, yes, I've conceeded that you couldn't provide a good moral justification. You at least got that right.