God-based morality?

Someone left a comment to God, Atheism and Buses at Washington Post.

You can't answer the paradox of God-based morality by defining obedience to God as morality. The counter is obvious: what if God told you to do something immoral?

You recognize the problem, and so answer the question by begging it. You say, God wouldn't tell me to do something immoral, and if he did, I would know it was not God.

How would you know in the first place if the requested act was immoral? You can't ask God; he just told you to do it. That leaves your own human-developed sense of morality as the only standard.

Neither can you say that a request to do an immoral act cannot be from God. That just shifts the question from whether the act is immoral to whether the act was actually requested by God. You have no way to answer the question if your only standard for determining whether that was actually God is determining whether the requested act was moral using your own standard of morality. [my emphasis]