Paul O’Mahoney at the Dublin Review of Books:
Nietzsche’s protest that one cannot cleave to a moral system originating in Christianity after denying the Christian God has implications far more profound than appear at first blush. Nietzsche could already see that purportedly secular doctrines in the ascendancy in his time, and which looked set to become orthodoxy – the sanctity and inherent dignity of human life, the fundamental equality of human lives – were in their origin and character inescapably Christian. It was an absurdity, he felt, that people should, at the moment of the “death of God”, cleave all the more fiercely to the doctrines which depended on Him; or to imagine that one could keep and could promote the gamut of Christian virtues – lovingkindness, humility, charity, counsels of gentleness or forgiveness – when the religious-metaphysical belief system underpinning them had been renounced. If one gives up the God, one ought also, or must also, for the sake of what Nietzsche called one’s intellectual conscience, give up the teachings of the religion. In this Nietzsche foresaw the coming orthodoxy of the late twentieth and early twenty-first centuries: secularised Christianity that calls itself by the names of humanism, egalitarianism, human rights, and which (quite unknowingly) preaches Christianity without Christ.
more here.