Not to throw fuel on the fire, but...
Once, while reading Aquinas, someone suggested that evil existed in God's world -- that is, he allowed it to exist, since he is good and could not have created it -- he does "more" good by bringing good out of evil, such as using a natural disaster to bring humanity closer together. Thus it is perhaps better to "allow" evil to exist so that good might be brought forth from it than to annihilate it outright and gain no benefit from its presence.
Twisted, yes, but God can do whatever the hell he wants, and we have to cope.