Yes, well poor Ron doesn't seem into that kind of thing as much as Kim. He freaked out when Kim got all Moodulated and tried to beat him up after all.
However, Kim's needs in a relationship with him are satisfied by his occasional bouts of her turning evil and attempting to beat her up, and of course, her trysts with Shego on the side. So it's never an issue between them.
...this reminds me of how dissapointed I am we never got to see Kim hit with that evil ray. The destruction she would have wreaked would have been glorious, as would have been Ron's reaction and Shego, of course, would have teamed up with her immediately, glad to have an equal to be psycho with.