It’s nonsense. Assuming omnipotence, there is no need for lessons, wisdom, pain or strife. All of the wisdom that we gain from those things, he could imbue us with. Allowing children to be raped is beyond reprehensible and could only be for his own curiosity or enjoyment. If any human allowed a girl to be raped, had the capability to prevent it, didn’t but felt bad you, would tell them to get fucked and do something next time. You only let your skyfather off the hook because it’s a cultural artifact you were raised with.
This is just an argument that boils down to Douglas Adams saying “The story so far: In the beginning the Universe was created. This has made a lot of people very angry and been widely regarded as a bad move.”
You can say it's not fair that God allows evil to exist, but you must admit you're arguing that the universe itself simply shouldn't exist. Our existence requires the existence of choice and choice implies that choosing the wrong thing is possible. Ask yourself what you would do if you had the power to stop all rape. Would you stop at just stopping rape? Would you stop
everything you deem to be evil? Would you accept arguments from other humans about what is or isn't evil? At what point are the humans you have such absolute control over no longer human and instead just little biological robots you've programmed to perform a nice orderly set of 'good' actions?
Further, would you go as far as to stop people before they perform the action in the first place? If we accept that the universe isn't deterministic (this could, scientifically, be the case), then you can't know what someone is going to do before they do it. Would you stop an action because it just
may result in something you deemed to be evil?
The logical conclusion of "God should not allow evil" doesn't hold water, especially since it always includes your personal opinion of what evil is. You can be upset about this or claim that God must be an evil being because your personal opinion of what constitutes evil is different, but merely saying "for God to exist, evil must not exist" is quite simply not correct and it has never held in any philosophical or theological debate, because again, the conclusion results in our universe not existing.