Self-censorship or just editing?

It is guilt, no question, because we find alluring ( in fiction) that which the more public parts of our minds condemn as totally unacceptable. Guilt certainly at hypocrisy, the fact that not every part of our psyche falls into line behind the things we'd like everyone to think we think.

If a story protagonist gets mugged and beaten up that's bad, it's assault isn't it? and probably "Actual Bodily Harm" as well. We feel affronted on their behalf. If however the same character is subject to a non-consensual spanking, probably with a nice swishy cane or a never-used-on-the-hair hairbrush that's a good thing; it isn't assault because we find the action of the spanking entertaining and / or arousing. There is nothing for it, we exercise serial double standards, and say it's OK because it's fiction.

The same reasoning doesn't quite apply in crime fiction where horrible things happen because most often the protagonist is the detective, and the crime is viewed as altogether a bad thing and the perpetrator is the villain. If the 'spanking story scenario' happens and the detective is assulted by the baddie that's still a bad thing, and probably would be even if the assult were spanking (with the notable exeption of the works of Mr. Barretthunter where the policewomen are routinely spanked, but these are spanking stories, not crime stories, so they come into the other genre)

However, I think that most folk are the same with regard to the double standards, we enjoy a more extreme situation whilst it is safely contained within the bounds of fiction, and this helps reassure us that our own world within the circle of our camp-fire is safer than that.
A tenet of fiction writing is that things need to be larger than life in order to overcome the natural dilution in effect which happens when ideas take the torturous route from one mind to the other. This is one of the reasons that spankings in fiction are more severe than they'd need to be in real life, (and why crimes in crime fiction are more dastardly)( again, with the possible exception of certain stories concerning Botswanan private detectives).
This leads to the use of the non-consensual as a means of increasing the dramatic effect, and other devices to increase humiliation etc.

I never find rape amusing, I find spanking amusing, panties down, red bottom, lots of wiggling and begging, embarrassment... that is amusement. Rape changes lives. And whether it is a Penn State Univ coach or a priest or minister or youth leader taking liberties with a young boy or a young female teacher on a bizarre power trip with a middle school student who falls under her control, it is all immoral and destructive and truly has no place as entertainment. I am grateful for the policy on this site that allows no sex with children, that is another disgrace. And I do understand when authors choose use rape to define a character as intrinsically evil. Still...

islandcarol, your phrase power trip gets to the point of the difficulty. Rape is a horror, and ruins lives, as the extreme form of sexual domination. But it's not the only form; nonconsensual spanking is precisely another--in reality. But here it's a fantasy pleasure, at least it is for me, & I'm not unique here I think! But it's only a pleasure when the aim is precisely not sexual, ie the aim is punishment. That's how it is for me. Is it wrong to be amused by a rape fantasy? It's not something I find amusing, but is it wrong in principle? JUst a question. In my early teens I fantasised about deserving women being kidnapped and spanked en masse, but that might just have been because I couldn't then imagine anything worse that could happen! Or perhaps it was just a way of displacing my guilt. So far as I can see, in reality power trips are always foul, whereas in fantasy they can extremely exciting. Goes back to opb's point above.

I just submitted an essay to the library about the morality of spanking stories, inspired by this forum thread among others. My thoughts on the matter ended up too long and complicated to post here.