When we share the begotten Son, we can point to the Nicene Creed, and then it is not only us who are speaking, but that whole great church council. It is an appeal to authority of the most powerful type, especially because most people agree that it represents early Christianity and (nominally) agree with it. It can give us confidence when people try to paint us as being loners who invented this new doctrine – we did not; we are not alone on this.
Remember these words in the Nicene Creed: "We believe… in one Lord Jesus Christ, the Son of God, begotten of the Father [the only-begotten; that is, of the essence of the Father, God of God,] Light of Light, very God of very God, begotten, not made…"