In order to understand this saying, you have to consider it from the perspective of the bluepill. From a bluepiller's delusional point of view, nobody has trouble having sex, or alternatively sex isn't that important. So therefore, what reason could someone possibly have to want to rape someone else? It can't be sex, because sex isn't important. Rapists are obviously also inherently evil, so their motivation must be evil. Clearly it is because they just want to oppress others.
On the other hand, when it is a foid saying it, you have to consider that to foids, all men aside from Chad are invisible. Therefore, when she thinks about a man raping someone else, she imagines Chad. Chad gets all the sex he wants, so why would he need to rape someone? Obviously regular sex isn't enough for him.
Another interpretation is that it is intentional intellectual dishonesty, they have an agenda against male rapists, or rather against men in general, so they want to vilify men as much as possible in any way they can. By hiding or discounting the fact that modern men are desperate for sex, they can act as though committing evil acts like rape is in the man's very nature, rather than the result of being driven there by his environmental circumstances.
This reminds me of a great quote I read once by Anatole France:
"The law, in its majestic equality, forbids the rich as well as the poor to sleep under bridges, to beg in the streets, and to steal bread. "
From the perspective of the law, it doesn't matter if you stole bread because you were starving or because you were just bored and wanted some excitement.
