Authority and Separation

In Leviticus, God tells Israel to be holy because He is Holy. In the subsequent verses, He gives them laws on the basis of His own authority. The explicit purpose of these laws it to differentiate Israel from the nations that they are to destroy. The reason for those nations' destruction is that they practiced all of the abominations that God forbids. So too, our society has degraded to the point that we have made all of the forbidden abominations commonplace.