The point of Nietzsche is that the death of Christianity meant that there is no longer any truth. Or universal truth. The Christian religion talks about universal truth, because it is self-evident. No god, means there is no truth, instead we create our own truths, or follow a truth among many. He did veer off into a distinct system until he realized that wasn't his main point. The point is, is to create a new universal truth, however, you create it. He had a disdain for contemporary atheist, even atheist today, who cling to morals attached to an extinct truth. Therefore, no rational, or coherent basis. They make an argument with literally no argument. In a way, he predicted a world after the death of Christianity of having no order, and people cling to movements such as fascism, communism, humanism, liberalism, etc.