What would be good etiquette if, as a man, the reason for this attitude during sparring (or any other sort of intense pair training) is mental discomfort with the idea of throwing even mid-level strikes with women? I've found myself paired with girls and it is quite uncomfortable to try and disregard this cultural norm.
I did that exact thing described of just using defence and letting the girls work their offence during these routine 'colosseum' exercises (I forget the English term for it) at a gym I trained at, where the instructor would make one of us (sometimes a woman) do rounds with almost everyone at a time. It wasn't supposed to be sparring, but eventually the one doing the rounds would get tired and more desperate, so they'd put more behind their strikes and, between men at least, you'd end up reciprocating with similar intensity. I use this example because, even if you oppose to being a sparring partner for a female (if your instructor lets you, that is), you might find yourself in a situation where you'll basically be doing light sparring with them, and might adjust your power a bit too low for those that want to be treated equally.
Sorry if this is a bit of a convoluted question, but basically I wanted to take the chance (and please do excuse me if I'm unknowingly derailing the topic of conversation) to ask what you think would be the right procedure for males that just feel uncomfortable hitting females but nonetheless get thrown in situations where you have to be available for them and actually want to help them improve their skills in any other way you can (as you would with any other training partner, since that's obviously the idea- to get better together). Thanks!