The two statements are actually very similar in content. Augustine is arguing that free will allows a greater possibility of good than its absence. It allows evil as well, but he believes the sum of good outweighs the sum of evil. Greenberg is making an emotional argument stating pretty much the opposite. There is no good, he implies, that can possibly counterbalance even this one example of evil. And if this is the case then free will can overall be only completely negative or otherwise motivated by some other factor. From there we might expand on why and how each of them adds up their moral calculus. An apologist such as Augustine might suggest that burning children create the opportunity for heroes who rescue them, police and judges to punish the evildoers, and so on. Or perhaps that the afterlife can more than compensate. A critic might suggest that no free will might mean no heroes, but that the NEED for heroes is itself an evil intrinic to the creation of free will and something a good god shouldn't be spreading around. Hope that helps!