If a historically disenfranchised group wants to have an event just for them, I'm fine with it. I don't have a problem with men only or women only clubs or social associations.
Sometimes you just want to go and kick back with others of your gender, talk and have fun without worrying about what the opposite gender might think or say. I get that and it's totally harmless. There are degrees to everything. Some degrees are acceptable, some are not. This is easily acceptable. This is not the same as real world discrimination.
Ask yourselves how many times have you wanted to hang out and talk to the guys without having to worry about women hearing and being offended? You know, just be men and clown and say whatever. Well, this is the same thing.
This is thee epitome of 1st world, white boy problems, here. ...lol