Evil and the burden of proof

You can accept the extension of the category "evil" to be whatever theists want. It appears to follow from essential theistic claims--that God, is the omnipotent, omniscient, creator--that evils exist only if permitted by God. It also appears to follow from the further tenet that God is perfectly good, that he will permit an evil only if he has a morally sufficient reason for permitting it. Consequently, every actual evil, i.e. every evil that God permits, is such that God has a morally sufficient reason for permitting it. But what possible grounds could anyone have for holding that for every actual evil E God has a morally sufficient reason for permitting E? No theodicist claims to be able to account for every evil, but only to give some justification for broad categories of evil. Yet a single actual instance of gratuitous evil, i.e. evil for which God would not have a morally sufficient reason, is incompatible with the existence of God. Theists must therefore have some basis for confidence that there is no gratuitous evil. What could that basis be? I suspect (sigh) that, in the end (sigh) it will come down once again to the "F" word: Faith.

http://secularoutpost.infidels.org/2012/08/advice-to-critics-of-argument-from-evil.html#comment-607792749

Parsons is illicitly shifting the burden of proof. Since the argument from evil is an argument which an atheist deploys to disprove God, the onus doesn’t lie on the theist to prove that no instance of evil is gratuitous; rather, the onus lies on the atheist to prove that some instance of evil is gratuitous.