I'm not a medical ethicist, but I believe any contact in a medical context without informed consent is wrong. This discussion and other threads here led me to check the policies of the medical schools and teaching hospitals in my state. Each one has a code of medical ethics that forbids the abuses of unconsenting patients described in these threads.
My research also led me to other places that allow these abuses and fight attempts by government to rein them in. I can not understand how any medical ethicist justifies some of these practices, especially when easy alternatives exist such as volunteers/standardized patients. The best rationalization I can come up with is that a patient is just a piece of meat and we don't really need to have any regard for them beyond that. It goes downhill rapidly from there (power and sexual jollies, rape culture, whatever you want to call it).
On to coerced informed consent in the case of students being asked to practice on each other. Would I want my female classmates practicing very intimate exams or invasive procedures like cystoscopy on me? Probably not, but I would let them. However, as a male I have far more sexual agency. If I had a vagina I would feel a lot differently about the situation. I might feel that it would be ok for other females to practice on me because it eventually leads to more empowerment for females in general.
When I was in my early twenties, my girlfriend's best friend was in a long since shuttered private hospital system's residential nursing school. She and her roommates and classmates practiced intimate area skills like enema administration and bladder catheterization on each other. They were obviously all female in those days and I'm pretty sure they knew what they were getting into. I know we have some members here that are nurses from that era. It would be interesting to know their thoughts on the ethics of that.
But I think in the modern era, its incredibly sexist to have the attitude “oh so you girls want to be doctors now and not just nurses… well, you have to spread your legs for your male classmates… its for science”. I'm really kind of surprised that still flies these days.