My understanding is that he's explicitly stated that this is his intention
If you could find a link I'd certainly be interested. I don't know; again, all I can do is repeat my general sense that when something is designated unmentionable, Moore will want to mention it. I'm certainly not denying that the character is rooted in repellent ideas, but... there are a lot of repellent ideas presented in LoEG. And I don't think The Black Dossier is aimed at children, so I'm not sure what the specific concern is.
I suspect that Moore was very aware that it'd be uncomfortable for some readers, and that we'd rather not run into that kind of character, and that was at least part of why he included it. I mean... we saw rape presented as comedic in vol 1, and as (more or less) just punishment in vol 2.
To be clear: I don't think it's silly for readers to find it uncomfortable and I'm not dismissing your personal reaction. I just think part of what makes him tick is an interest in figuring out what makes people go "Oh dear, you can't DO that."