while it is true that reality as experienced by man is subjective (sense of time, space and so on) and the true nature of reality cannot be fully experienced or reasoned by primitive meat-vessels such as ourselves, reason still demands that objective reality exists outside of our subjective perception, so there are fundamental truths regardless of our inability to comprehend them.
Morality independent of theology and metaphysics, based only in reason inevitably leads to the death of God. Once this occurs morality becomes vulnerable to criticism. Consequently secular rational morality is hollow, being a mere rigid command. One can't justify such a command as the ground upon which one tries to reason is like quicksand. Without an absolute basis for good and evil moral norms are whatever suit the individual for it's own advantage. Basically "you can do whatever, it does not matter as there is no absolute truth".. nihilism.
Nihilism, this bourgeoise disease of the soul is what plagues people today, their lives misery in affluence, depression, lack of meaning and hope. We thought traditions chained us, we wished to be free.. little did we know the chains nourished us and without them we are lost and dying of thirst in the desert of absurdity.
Everything is permitted. Man has failed to become God. Man is misery incarnate.