'Sharing'
A man using a women's space is not 'sharing'. As soon as a man enters a women's space it is mixed sex. It becomes a space where women's privacy, dignity, and safety are compromised.
Mixed sex spaces are more risky for women. We are entitled to privacy, dignity, and safety, and no we won't sacrifice our privacy, dignity, and safety because you think it's not 'that bad' if women are frightened, intimidated, threatened, triggered, uneasy, etc.
Men in men's spaces are evenly matched in terms of size, weight, muscle strength and likelihood of criminality. Even men who really don't want to use men's spaces are male and as a class, not at a disadvantage comparison to women. Males also don't have the risk of pregnancy that women have.
On this green earth how could anyone suggest a man who is of the sex class that is larger, stronger, commits 80% of violent crime and 99% of sex crime, should be put in with women, because he wants to be?