Do you think it's wrong that I supported the boy scouts until they started admitting girls?
Maybe if that is what made you stop supporting the Boy Scouts.
What they're doing is no longer segregationist
It's okay to want things to remain stable and predictable, but it's not okay to support leaving girls out. Girls should have the same opportunities as boys to learn new skills, so you shouldn't take that away from them by refusing to support the Scouts.
I'm fine with girls joining boy scouts, as long as they are segregated from the boys.
Well segregating them from the boys creates an unequal learning environment. For them to have the same opportunities they need to learn together.