OTOH, Ranma in this story is coerced into an unwanted
marriage, complete with sex. To put it himply, he's being raped. And the
idea of a rape victim turning around and liking it because the sex is so
good offends my sensibilites like few other things can.

Genma and Soun were trying to coerce Ranma into an unwanted marriage, complete
with sex, in the canon series.  The only differences being that the coercers
weren't the bride, and that Ranma grew to like it before the sex rather than
after.

If being coerced into an unwanted marriage is rape, you may as well forget the
whole premise of Ranma 1/2.