They are people, not objects for your pleasure. If your comment even remotely reflects your attitude towards them, then you might as well have been telling them "GET OUT! WE HATE WOMEN!".

Do you think that maybe if you treated them like people and welcomed them to the group with patient explanations, expecting nothing, they might have hung around?

I at least try to never ascribe to malice that which can be easily explained by incompetence. Geeks are not known for their social skills. Their reclusiveness and cliquishness limits their ability to learn social skills from their more skilled peers, instead trying to learn from each other, like the blind leading the blind. Combine that with hormones and even more limited experience dealing with women as people and you get them either trying to one-up each other in some of the sort of dick measuring contests they use as social dominance displays or using patronizing gestures to treat women as if they were children.