One of the important conceptual disputes between Augustinians and the classical universalists is the manner in which divine-human relations are understood.
For Augustinians, human beings are not always treated by God as ends in themselves. Some persons exist for the purpose of the expression of God's justice at their expense through their deserved eternal damnation. It might be wrong for humans to treat other humans merely as means, but it would not be wrong for God to do so, since he is in a higher ontological class than humans are.
The classical universalists, on the other hand, were convinced that God always treated humans as ends in themselves, because he loved them. The divine philanthropia, love of humanity, is what motivates everything God does -- whether punishment or blessing or whatever. On the other hand, for God to create some persons for the express purpose of damning them is morally abhorrent. St. Isaac in Ascetical Homilies II/39, 2 says that such a position is "unspeakably blasphemous," a product of "infantile thinking," and a calumny against God.
Who is right?
For Athanasius in On the Incarnation, 6 it is the reality of the image and likeness of the divine Logos in human beings that confers upon them inestimable value. Because they are made in the likeness of the Logos, reasonable and rational, it would be (in his words) "supremely unfitting," "monstrous," and "unworthy of God's goodness" that his creatures be destroyed -- whether deservedly or not. There is obviously room in Athanasius' theology for the punishment of the wicked, but evidently not in such a manner as would preclude treating humans as ends in themselves. The fact that humans have a piece of God in them precludes God, in his goodness, from destroying them or leaving them to perish.
Jesus said, Consider the ravens: they neither sow nor reap, they have neither storehouse nor barn, and yet God feeds them. Of how much more value are than the birds!
Can we plausibly add to this statement: ... Indeed, you are much more valuable, but not so much more valuable that God could never make an example of you by predestining you to eternal damnation for your sins, so that others might know God's justice and appreciate their salvation even more ? My sense is that this would too radically compromise the strength of Jesus' exhortation not to worry.
Thomas Aquinas wrote:
And just as He does not enlighten all the blind, or heal all who are infirm, in order that the working of His power may be evident in the case of those whom He heals, and in the case of the others the order of nature may be observed, so also, He does not assist with His help all who impede grace, so that they may be turned away from evil and toward the good, but only some, in whom He desires His mercy to appear, so that the order of justice may be manifested in the other cases (Summa contra gentiles III/161, 1).
We have to ask the question whether this is plausible. I grant that justice or fairness is a good thing understood abstractly, but is punitive justice -- the deserved punishment of the wicked -- a good thing in itself, something to be desired for its own sake? To my mind this is not plausible. Punitive justice is something we want only on the condition that people are committing evil. It's a conditioned good thing; it's a good thing that can come out of a bad situation. But it makes no sense to my mind to suppose that punitive justice is something that you would want for its own sake, even if it could be avoided altogether. Punishment of crime is something we have to plan for because it is inevitable, given the fallen condition of the world and of human persons. I don't see why a person would plan punishment for crime if there were no necessity or chance that crime take place at all. Human persons are more valuable than that; they are to valuable to be created solely for the purpose of being made an example.