I too, respectfully, differ from the survivor self-help lexicon. I do think rape is sex - for the perp, not for the victim.
Sex and violence are not antonyms. I think even the most straitlaced, vanilla, procreation-only individual will have noticed that there are elements of power and, if not dominance, then at least authority involved. It is betrayed by even the most clinical terminology we can use: "pursue," "active," "receptive," "penetrate." The change in tone of voice and the words used - the promises, sometimes warnings. Don't think I need to spell it out more graphically, we are all adults here. To a major extent, sex rotates around power. And again, that's strict strict vanilla. The existence of the BDSM community speaks for itself, as does the superabundance of rape fantasies. People are very good at eroticizing dominance. At least for themselves. That doesn't make it any less of a crime, but if it involves fucking somebody then it is about sex for the aggressor.
A recent anti-rape PSA campaign in Edmonton succeeded in reducing sexual assault rates by 10% just by pointedly clarifying what is and is not valid consent (ie "sober on drunk" is not consent, it's rape). The fact that the rape rate dropped after this proves that there is a non-trivial segment of the rapist population that actually just was after sex and thought they were doing it the right way, but then changed upon being told otherwise. If it was all about violence, consent would never matter and the rate change would have been zero.
"Don't think it hasn't been a little slice of Heaven just because it hasn't!" --Bugs Bunny