This makes me think of a rather colorful college professor of mine who has been shooting nudes for 40+ years. He always incorporates fully nude shoots into his Intro to Photography classes (designed for the normal non-photo students taking it for their art elective) and puts the dates of each shoot into the syllabus.
He mentions that nude model shoots will be part of the corse the first day and reminds them again a week prior to each one. Of course, all the guys in the class get excited to the idea of shooting a fully nude woman, or, even better, women.
However, what he does not tell his class, until they get there, is that the first one will only have male model(s), and of course plays it off as if why should it matter?.
Anyway, I see no problem with this and think the complaining is a gross overreaction.
Maybe the way in which it was marketed and advertised was a little creepy, but (follow ups show it was a small event that was not advertised in a creepy fashion and open to only a select few) all fashion photographers I've known always want to fool around with skin tones and lighting the body. Not to mention, skins tones (along with other natural tones like wood, something I need to worry about with my line of work) are hard for the camera to naturally reproduce and something photographers will want to test out.
Insofar as not having a male model, having one could have certainly helped with it being less sexist, or perceived as being less sexist. Would it have helped with drawing more people? No; much less women go out of their way to see a man naked as vise versa. Not to mention, our society puts more emphasis on the female form being the superior one. (You have to go all the way back to Ancient Greece to see it the other way around.)
Also, the average woman is naturally more curvy, which helps with producing light and shadow and gradients. The average man is rather boring, flat chest, flat ass, hips and waist that are almost equal. You kind of need someone built like Atlas to really get nice light and shadow.