At our Dojo (MMA) during boxing sessions (we had guys and gals), sometimes I would box one of the women...but was always gentle, slowed my punches, hit lightly to avoid hurting them. Helped them learn to hit and block w/o injury and made it fun for them. They liked me for that.
During promotion time, we had to demo the required techniques and after that, fight a stronger opponent (often one of the instructors). Tradition was that the instructor (assistant Sensei or a senior student) would beat the crap out of the student qualifying for promotion.
When I was up for green belt, so was a young woman student. Sensei had us fight each other. I was about 5 or 6 inches taller and about 50 lbs heavier. 3 minute match. I went gentle mode and slowed my moves down. Asst Sensei not happy about that but the senior Sensei (Dojo Master...a 7th Dan) allowed it and we both got our green belts.
I just can’t see any virtue in beating up women.
Your sensei was correct. Misuse of power is no sportsmanlike behavior. We put people in jail for beating up women. The Olympic committee is giving them gold medals.
I blame the start of this on those video games in the 90’s such as depicted in the 2003 movie Bad Santa during the shoplifting scene. They depict girls fighting martial arts style and winning over men. This totally blurred reality.