It can also be argued that the best proof of God's love for humanity is that he allows humans
free will.
Yes, this sometimes means that they will perpetrate great evil upon one another. But the good that comes from free action is far more valuable than that which is forced- can we even say that a man is good when he does good things only because there is a gun against his head? He isn't actually doing them- the man with the gun is telling him what to do. There's no good in that, only self-interest.
Now, if you believe that all actions are predestined, and that human will plays no part whatsoever in actions taken on Earth, then I can see the logic. But otherwise, it only makes sense that evil would be allowed to exist, because you cannot have ultimate and meaningful good without the temptation of evil.