The joy of folks in heaven far outweighs the suffering of folks in hell. Evil is due to Satan. But God lets him go around doing evil and tempting people as a way of testing their faith, and making them stronger. Evil due to original sin. We can consider this to be a version of the free will defense.
People can do evil.
If there is no logical impossibility in a man's freely choosing the good on one, or on several, occasions, there cannot be a logical impossibility in his freely choosing the good on every occasion. Clearly, his failure to avail himself of this possibility is inconsistent with his being both omnipotent and wholly good. Mackie seems to be rejecting the libertarian conception of freedom. You could have done otherwise. It doesn't matter that you couldn't have done otherwise.