From what I read that Caroline venue (which is near my work and is kind of out of the way of the bulk of the entrainment sector, I've never been there though) isn't saying that the band needs to have a female member but have a non male perform with them for just one song which is much more reasonable and less discriminatory than suggested.
I think this is an excellent policy designed to increase the number of wahine performing at our venues in the city.
BATS have also programmed predominantly female comics for the Comedy Festival which is even more awesome.