Is it acceptable to ban men and white people from a student meeting?

I have just listened to a discussion on Matthew Wright's show regarding a meeting held at Goldsmiths University where a female "Diversity Officer" requested that males and white people stay away from an equality event, no irony there! The general consensus of the panel that this was not on and Matthew Wright argued robustly with a listener who phoned in defending the exclusions. Whilst I can understand there would be issues that would only be pertinent to women where it would be justifiable for it to be a "women only event". Is it ever acceptable to ban people on grounds of race and sex, particularly from a meeting which I believe was supposed to be about diversity