X sansmerci
We live in fundamentally racist society that still operates on the "one drop" principle, even if that is never vocalized or acknowledged, pretty much.
It sucks, largely because it's so ingrained that anyone called out will probably refuse to see it, act like you are crazy and/or have just called them actively evil, not called them out on the conversational equivalent of having something in your teeth.
Very much this. If you look at all dark, people will tend to call you black. If you look white but they find out your grandmother or some such was black, even if you're only like 8% black, they will call you black. As ridiculous as it is, that's generally how it goes. They should move to a percentage system or else a system that allows your "race" to be multiple things at once like it actually is.
But that's too messy and inconvenient.