I'm ashamed to say that I used to have the rape fantasy thing. With me, I think it was more that I was fighting the whole same sex attraction thing and being taken against my will would then be someone elses fault, not mine.
I can honestly say, that when real life struck and it happened, that fantasy completely disappeared and now I even have a difficult time with any type of dominance during sex. My last gf liked having her hair pulled hard during sex, and I couldn't even do that comfortably.
you shouldn't be any more ashamed then the women with the same fantasy
btw it is one of the most common sexual fantacies amoung women