When my mom was in elementary school in the 50s, the nuns used to whack her with a ruler to make her write with the right hand. It's about conformity. Gingers absolutely were and are treated poorly in the UK, no idea why apart from general clannish racism. Certain physical characteristics take on cultural meanings that we wouldn't necessarily relate to, like when a woman had blonde hair in Italy. Not that any of those things are comparable to the experience of being black in America.