Hold up, that’s a separate issue. Revenge porn is flat out illegal, so using nudes of people, real or not, as blackmail, isn’t up for debate here. Whether or not it’s obvious, and I’m sorry if it’s not, I’m 100% with you that that’s completely disgusting and shouldn’t be tolerated.
Back to the first part though, is the problem literally just that it exists outside of the persons head? If they don’t share it with anyone, what’s really the difference from them imagining it? In both scenarios they’re effectively getting the same result, and nobody else is affected.