Nick Trakakis and Graham Oppy raise the same objection:
Firstly, the theist may agree that Rowe’s argument provides some evidence against theism, but she may go on to argue that there is independent evidence in support of theism which outweighs the evidence against theism. In fact, if the theist thinks that the evidence in support of theism is quite strong, she may employ what Rowe (1979: 339) calls "the G.E. Moore shift" (compare Moore 1953: ch.6). This involves turning the opponent’s argument on its head, so that one begins by denying the very conclusion of the opponent’s argument. The theist’s counter-argument would then proceed as follows:
Although this strategy has been welcomed by many theists as an appropriate way of responding to evidential arguments from evil (for example, Mavrodes 1970: 95-97, Evans 1982: 138-39, Davis 1987: 86-87, Basinger 1996: 100-103) – indeed, it is considered by Rowe to be “the theist’s best response” (1979: 339) – it is deeply problematic in a way that is often overlooked. The G.E. Moore shift, when employed by the theist, will be effective only if the grounds for accepting not-(3) [the existence of the theistic God] are more compelling than the grounds for accepting not-(1) [the existence of gratuitous evil]. The problem here is that the kind of evidence that is typically invoked by theists in order to substantiate the existence of God – for example, the cosmological and design arguments, appeals to religious experience – does not even aim to establish the existence of a perfectly good being, or else, if it does have such an aim, it faces formidable difficulties in fulfilling it. But if this is so, then the theist may well be unable to offer any evidence at all in support of not-(3), or at least any evidence of a sufficiently strong or cogent nature in support of not-(3). The G.E. Moore shift, therefore, is not as straightforward a strategy as it initially seems.
…it becomes clear that the vast majority of considerations that have been offered as reasons for believing in God can be of little assistance to the person who is trying to resist the argument from evil. For most of them provide, at best, very tenuous grounds for any conclusion concerning the moral character of any omnipotent and omniscient being who may happen to exist, and almost none of them provides any support for the hypothesis that there is an omnipotent and omniscient being who is also morally perfect.
I find their objection rather odd:
i) The argument from evil is primarily an argument against God's existence, not God's benevolence. So evidence of God's existence, apart from the question of evil, certainly seems germane to the overall force of the argument from evil.
ii) Perhaps the objection is that in the argument from evil, the concept of God is the concept of a benevolent God. Therefore, the argument targets that particular concept of God. Unless he's benevolent, he doesn't exist.
a) But although that distinction may be useful for analytical clarity, it artificially separates evidence for God's existence from alleged counterevidence based on evil, as if the latter discounts the former. It's not as if atheists believe in God, only they think he's evil. It's not as if they think there's evidence that counts for God's existence, as well as evidence that counts against his benevolence, so they affirm the existence of a malevolent God. Hence, they can't use the alleged evidence of unjustifiable evils to simply cancel out evidence for God's existence.
b) Assuming that God's existence and benevolence are inseparable, isn't that reversible? If there's evidence for God's existence, then this might indicate that evil, even if it constitutes some prima facie evidence against God's existence, must be counterbalanced by other lines of evidence. Put another way, the incongruity is only apparent.
c) Apropos (a-b), evidence for God's existence could be combined with skepticism theism to circumvent the argument from evil. Even if (ex hypothesi), evil constitutes prima facie evidence against God's benevolence, if there's positive evidence for God's existence, then why not take that to indicate that God is, in fact, benevolent, God has a morally sufficient reason for evil, even if we can't discern it?