If we need God to exist in order to have a transcendent moral standard, then if we reject God, we lose the right to make moral judgments. Imagine being unable to say for sure that anything was objectively wrong. Some people who deny transcendent moral law have recognized that their moral judgments no longer have weight.
In an interview, atheist Richard Dawkins stated that our value judgments are the product of evolution and therefore random and arbitrary. He admitted that his belief that rape is wrong must be as arbitrary as the fact that we’ve evolved to have five fingers instead of six. If we’re intellectually honest, we must admit that denying moral law disallows us from making moral judgments.