Well, it's rather simple to me.
Men calling their victims names usually (want to) achieve two things by that.
By degrading the victim (in those cases usually a victim of a higher social stand) they pull her down to their own level (even if only a felt level, not an actual one) - even further down. Such women - as I feel I am among them - are even more humiliated by being called those names as if "just" raped only.
Since most rapists are cowards with very low self-esteem - leaving out rare exceptions which occur - they boost their self-esteem even more when they put their victim down and force her "below" them. Same as highschool bullies when they pick on the "weak" to make themselves feel better.
In fantasy it's just another tool of additional humiliation and degradation just as raping a woman anally usually is. It's a tool of exercising power, of abusing her verbally and mentally as well, aimed at making her feel even worse about herself.
Others however actually prefer "high-class" targets, not necessarily out of low self-esteem but rather a possible hatred of the better classes or maybe - because they make a more high-prized prey and taking her even more outstanding since such women are usually harder to get to and wouldn't most probably under normal cirsumstances never meet up with a guy of a lower social status.
The male fascination with hookers or "slutty" women however is usually based on an evasion of any possible feelings of guilt. Raping women "asking for it" or selling their bodies anyway to anyone "who deserve no better" protects rapists from accepting responsibility or any feelings of wrong-doing. It also offers them an excuse if the woman was "leading him on" so the man can protect his own mind from accepting he actually raped someone.
Women who start off by calling themselves whore, slut, ... whatever may suffer from low self-esteem themselves so they put themselves down right from the beginning; some of them however use this measure as a tool of attracting men from the beginning, just as entering a forum posting sexy pictures of themselves or describing perfect "vital statistics" for example.
When it comes to virgins ... well, what man isn't fascinated with the idea of having a virgin (being a virgin usually being considered an exceptional sign of innocence)? And defiling a virgin is the ultimate fantasy for many men. On the one hand he knows he's not only raping her but also taking something from her nobody can ever give her back or get from her again, on the other hand it's the male fascination with destroying something pure - a very primal but still present urge in many male specimens.
Alright, whatever I forgot I might add.
