I love this post. I felt like it was very well written, accurate, fair, and unsensational. There are several things that it caused me to think about.

You said-

The atheist who wishes to contend that their sense of morality is based on objective truths, rather than subjective feelings programmed into them by evolution and their environment, must either accept the existence of an all-powerful god or justify the objectivity of their morality in a philosophically-sound manner.

Have you seen an example where an atheist has been able to "justify the objectivity of their morality in a philosophically-sound manner"? I would love to read or hear an example that you have come across.

Also, I wonder if subjective-moralists are able to separate their emotions from suffering better than other people in existence. They can rationalize that all suffering is only based on false assumptions of intrinsic value, ownership, rights, expectations, etc... If we were all subjective-moralists, we could cause and receive pain without emotional baggage knowing that all of the feelings we are being affected by are based on unimportant social, environmental, and evolutionary constructs(the use of the word "unimportant" is used in an objective way).