In time, a most unholy communion would occur.  The relationship between the Creator and his creation is a holy one with certain rights and privileges belonging to God alone.  A human example of this is the custom of asking a woman’s father for permission to marry her.  Bypassing permission and not respecting this order can have dire consequences (Genesis 34).  Marriage is intended to be between a man and a woman with the intention of creating new life.  Moreover, the holy consummation of marriage is intended to occur according to God’s design and not human innovation.  The same holds true for the rest of nature: reproducing and filling the earth in a manner pleasing to God.  We are spiritual and physical, and there are supernatural and natural aspects to reproduction which all must be respected according to a healthy conscience and God’s provision.  A group of angels would violate all of this.