Nobody said anyone was horrible. It's just that if a group is very dominantly male or female, you feel a bit like an outcast when you are the other sex joining in. Even if they are super welcoming, it's still feels a bit weird.

Also, each sex tends to have a bit of a difference preference on how a meeting-space should be. For example: Most of my male friends tend to hang out in garages/sheds some of the time. Never seen a woman choosing a those locations.