This really gets to the heart of it. Does anyone truly believe that laws should have nothing to do with morality? That the Church has no rational reason for what she believes and proclaims as the moral truth other than "God says this is bad"?
The Church, as the voice of Christ on earth, teaches us not only that God says things are bad, but the reason why. Her critics would do well to inform themselves of the actual reasoning behind the teachings. They may be surprised to find that it makes intuitive sense.