Touching somebody on the buttocks would be inappropriate for either sex but a push on the saddle or the small of the back is fine. You're ignoring the joyful comradeship of cycling and the spirit of friendly cooperation it engenders and reducing it to a miserable, small-minded exercise in political correctness. There should be no place in sport for that kind of negative attitude.
Two mountain bike clubs I know of in Lancashire were attacked by someone of that ilk, it went to Court and I'm delighted to say that the Court threw the case out and awarded costs against the plaintiff.