It's a derailment because the people bringing this up aren't actually organizing towards helping homeless men. These two issues, women's shelters and men's shelters, aren't actually in contradiction with each other but the commenter I was responding to is treating it that way.

The reason women's shelters exist is because activists in the 60's and 70's decided to build them and gain support, and eventually fought for funding. What is stopping any of you from actually building a movement to help homeless men, instead of complaining about the activists who try to help women in need of housing?

Why complain about the activists who focus on women's shelters because they're not ALSO tackling the issue of men's shelters, when you yourself could prioritize the issue of men's shelters?

Edit: The people who are dedicating their lives to helping homeless men do not see women's shelters as competition, they see women's shelters as valuable resources for knowledge with lots of carryover (such as approaches for addressing mental illness, drug addiction, and poverty). If you yourself have zero interest in putting in real effort towards a solution outside of opportunistic internet comments, why should anyone listen to you?

Take the lead, do some research, and build something.