"Show me just what Mohammed brought that was new, and there you will find things only evil and inhuman, such as his command to spread by the sword the faith he preached." - Manuel II Palelologus
Oh, they do know that this is the essence of a family, the basis of raising the next generation, and the basic building block of a stable society. This is the point, disrupt society so that we'll accept authoritarian socialism.
Look at all the policies of the left - they have the effect (and intent) of destroying the traditional family.