Why do you act as if the lack of absolute morality within atheism has any bearing on the alleged truthfulness of Christianity? That is a fallacy of appeal to consequences.
A Moral Argument for God’s Existence
- Absolute morals require a transcendent Moral Law Giver
- Absolute morals exist (e.i., murdering for fun is always wrong, everywhere, at all times)
- Therefore, a transcendent Moral Law Giver exists
The argument is not meant to prove the Christian God, only the existence of a personal, moral God. Other arguments help determine who God is.
“In logic, appeal to consequences refers only to arguments which assert a premises truth value (true or false) based on the consequences; appeal to consequences does not refer to arguments that address a premises desirability (good or bad, or right or wrong) instead of its truth value. Therefore, an argument based on appeal to consequences is valid in ethics, and in fact such arguments are the cornerstones of many moral theories, particularly related to consequentialism. ”
So the argument is valid in ethics, but this is not even an issue because the appeal to consequences argument structure is different than the moral argument anyway.
Also from Wikipedia:
- If P, then Q will occur.
- Q is desirable.
- Therefore, P is true.
For more on the moral argument, click here.