Sarcasctically, because one is in real life and the other in a computer, and you aren't being excluded or hurt from anything tangible. But I suspect you mean what if there were a town in real life that excluded men.

I think the inherent threat of violence would be a pretty clear difference between the the real and imagined scenario. I've been near a house with white power banners all over it in the south, I'm white and a man, and I felt threatened. I imagine the people those bigots hated would feel so much worse, more than I can realistically imagine. The threat of violence is inherent with racism everywhere, but in the rural US south, that racism carries more intent to do harm.

I do not imagine a town of women excluding men and by doing so imply they would hurt me or kill me if I came near or wandered into their town on accident. And I am a white man as I said before. Now if they also excluded trans women that would be a more clear indicator of bigotry and intent to harm.

And going back to the community you first mentioned, it doesn't allow men for the opposite reason, as I interpret it. It is to protect the women in the community from men who are much more likely to be a harm to the people inside. Because men are used to being allowed to go anywhere and everywhere, being gently told, "hey this discussion isn't for you, but you're welcome to sit and listen if you're quiet" is interpreted as an explicit act of violence, even though it's clearly not.