Fantasies of rape, domination & submission, and being helpless & taken advantage of are very popular for both men and women of any sexuality. There are too many sex operators, too much porn, too much erotica, and too many sex clubs featuring themes of domination and submission (for every sexuality) to think it's rare. And there are more still, like I know a woman who is mostly asexual but sometimes wakes up after a dream of being molested & abused and is incredibly horny (which fills her with shame and self-disgust but she can't help it) and she never avails herself of all the sources and clubs that cater to such fantasies. And when I've seen people anonymously share their secret sex fantasies I'm surprised by how many want to be dominated and abused. Truth be told, I feel weird that I don't have such fantasies! (And even so I've indulged others with such fantasies, playing the abuser or the victim as preferred.)
Of course such people are in full control of what happens in their imagination and not truly being harmed so it doesn't mean they deserve to raped or abused (where there is no real control and where actual harm & trauma can actually happen). If anything, I'd think someone who fantasized about being raped would be even more traumatized by it actually happening because of guilt and/or belief that maybe they wanted it to happen and brought it on themselves. And I knew a woman who enjoyed rape play (where she was the victim) but she hated actual rapists.
I have my speculations on why such fantasies are common (mainly based on Jungian psychology) but it's pure guesswork, and I also believe that the level of shame over one's sexual nature (which I've never experienced though enough tried to make me feel shame--I did grow up in Texas after all :tongue
and feelings of being overwhelmed by one's sexual nature probably contribute to it, too. But I don't want to bore you with my thoughts, especially as I'm probably wrong anyway. :redface:
But please don't feel ashamed for having such fantasies. Shame isn't helpful in this case. I don't have such fantasies but I don't think people who do are bad, and I've indulged such fantasies willingly enough without any judgment at all.