I wouldn't capitalise it, I think it's more analogous to black and white which I also wouldn't capitalise when used about race. In general I would use a capital for groups that are described by national or continental origin, but not groups that are described by a characteristic. In English, country names and the derived adjectives (France, French unless for windows) and organised religions are traditionally capitalised. (In French, the adjectives for countries are not.) To add an element of confusion, I wouldn't capitalise indigenous or aboriginal. Except for Aboriginal/Aborigine in Australia which has become a name, not just a description. I don't see gay/Gay as an issue to go to the barricades about, though!