The point of double blind isn't to get around your crazy scenario, but to be able to say you evaluated the effect of one factor on your self selected group Whi

The point of double blind isn't to get around your crazy scenario, but to be able to say you evaluated the effect of one factor on your self selected group Which generally ends up being that lots of studies are about isolating the effect of one factor on young white educated men, but you can at least say you've isolated the factor as opposed to just comparing young white educated men to the general population