What?! Are you serious?
They're real racial categories. If you have to understand the origin of the terms/ideas. In America, in 1500s, there were 3 races: Indians, Whites, and Negros. Each came from differnt regions of the world, and each were very related to each other(Mayans are very related to Cherokee, Spanish are very related to British). Those racial categories are genetic realities. In America, up until very recent times, pretty much all Americans were white or black(who all lived in the South till 1900s). These were/are very real genetic/racial categories.
Ashkenazi Jews are differnt in significant ways to Irish, but the ancestry they share is what makes them both "white". First of all just being from West Eurasia is very significant. Also, most Ashkenazi jews do have 374F, unlike anyone in the Middle East, and they did receive this via European admixture. Their Light skin certainly is of mostly European origin. Ashkenazi Jews are 20-30% North European-like. They have significant European ancestry.
For Papuans and Africans it's differnt. You're right they share nothing(besides being humans) but both look "black". However how many Papuan tribesman live in America? The Blacks of America, have always been the descendants of mostly West African Slaves brought here 100s of years ago. Only recently did some(still very few) African immigrants come here.
Yeah, but Blonde is still not a race. The "stupid Blonde" sterotype was never used to make fun of Swedish. It was created by Northern European-descended English speakers to referee to other Northern European English speakers. It never had anything to do with ethnicity or race or whatever. It's like making fun of people who are tall or have big noses.
That's differnt, because everyone in Africa has that hair and they're some of the only humans with it. It;s referring to a race, while making fun of Blonde hair isn't. That's comparable to saying people with white skin are stupid.