That’s why they’re so hung up on race / gender / sexuality: those things are caste markers to them, and determine the right and proper role for people in their eyes. If someone steps out of their pre-ordained caste, that’s violating the hierarchy and eroding the rules that keep society ordered-therefore-safe, and therefore inherently immoral to them.

You’ve nailed it. Also, if people start to realise these labels aren’t as fixed they may naturally extend those conclusions to other arbitrary markers - like class and wealth.