I would argue that the one about 'a black man in the white house' was in fact gendered, though it is somewhat debatable. It was referencing Barack Obama specifically. If there had been a black woman president, the phrase would have definitely been written to specifically say 'a black woman in the whitehouse'. On the other hand, if it had been written before either a black man or a black woman had (tried to) become president, it may have still used 'man' in a gender less way.