A common argument for the Trinity (or at least the eternity of The Son) is that God is love,
For if there be a being without beginning, existing before all things, was He loving when there was nothing to be loved? If through that unthinkable eternity He is lonely, what is the meaning of saying He is love?
G.K. Chesterton - The Everlasting Man - Part 2 - Chapter 4
and thus there must have been an object that could be loved by him throughout all eternity. The Trinity's idea of fellowship within unity seems an attempt to deal with this issue.
If Jesus the Son of God had a beginning, then it follows that before the existence of the Son, God being solitary, would have no object towards which to express his love. Without having anything to love, it seems God could not rightly be called “love” or possess love from all eternity.
How do non-trinitarian Christian denominations (mainly those who believe in One God the Father) respond to such an argument?