Rape and NTR is about power and dominance. In the case of tape its power over the woman, and NTR its about both power over the girl and either dominace over the cuckold or the desire to be dominated as the cuckold. Ugly Bastard is an extension of this desire for dominance.
The attraction lies in the readers perception of their own powerlessness (or unattractiveness) in the face of the object of their desire. A man who cannot convince the object of their adoration to desire them in return often finds fantasies of taking by force or guile what cannot be had through charm or ability attractive.
For women, there's sometimes a desire to be taken, for her patent dominance in the sexual economy to be disregarded. Sometimes a woman is the product of a repressive family/society and the fantasy stems from a desire to have (socially unacceptable) sex without the stigma of guilt (after all, if she didn't consent, then its not her fault, she is without sin because she was forced).
Of course, actual rape is a terrifying and disgusting act that even the majority of those who fantasize about it find repugnant.
Similarly some people find the idea of being degraded or debased itself to be attractive. Men who enjoy being cuckolds often also enjoy fantasies of being sissified (forced to act like/be turned into a woman) and of femdom pegging/male rape.
