When women who sign their names as women respond, the men often ignore them, or brush them aside with jokes about their incompetence.
Some women report that they receive very nasty and personal private messages.
Maybe women are more sensitive to flames than men are. But IMO women get flamed more often than men, in mixed groups. So women-only mailing lists can be vital lines of communication. The presence of porn websites does not bother me that much-though some women are very uncomfortable with the idea that they might encounter sexually explicit material accidentally. That automatic shunt kind of bothers me, especially if the site sets a cookie.