You refer to Kant believing moral facts constituted by rationality. I forget Kant's exact position, but I think morality can be based on reason without belief in religious imperatives, as follows. We find ourselves in this world with others. We note we are genetically programmed to be selfish. We see it's absurd to believe every human is #1. So it's rational to believe all people deserve equal respect. It's irrational to believe my needs supersede yours. The rest of morality follows from there. Ironically, the above egalitarianism was taught by Jesus. Arguably, theists attached theism to his teaching because they felt morality needed a theistic basis. His teachings work fine without belief in God.