There is also a different between "explicit" and "implicit" safe spaces for different groups. Its just that they are only ever "marked" with a demographic identifier if they are for a non-dominant group. I.e., "Comic Book Shops" are geared towards (historically, typically) white boys, but "Black comic book shops" and "Girl comic book shops" also exist. We notice these, because they are marked as such, because they run counter the norm. What we don't always notice is that the unmarked "Comic Book Shop" is already geared towards a particular demographic—white men.

Basically, different safe spaces exist for different demographics, but are only marked for certain groups.

Take Boy Scouts. It used to be exactly the sort of group that GP describes. Now that's been destroyed; the boys have been told that no, you can't have a boys-only group or event.