This is actually one of the things I am both positive and negative about. I think people are far more similar than sometimes assumed here. The evidence is pop culture. How could something be as popular as Star Wars or Metallica if not for calling out to a very similar underlying emotional hardware in people? In a No Mind Is Typical universe there would no universal mind product - there would be no hugely successful bands or movies just thousands of mini subcultures with mini stars.
One of my most surreal moments of How We All Are Really Alike was reading a documentary novel from an Afghanistani woman writer. I don't really remember the title or her name but I can find the book later if interested. Anyway she wrote Titanic was a huge underground success there. Underground because banned like most Western stuff, it was the early Taliban era if I remember right but still pretty much ever woman or young man saw it. It is a romantic movie that has just about NO reference whatsoever to how love or marriage is done in their culture, and yet it "clicked" because it talks to the same, universal human hardware. (Nm the book I found another source anyway.)
The important things is not whether you agree in the abstract with the fact that people are or aren't alike. The important part is actually noticing when you hit a topic where people aren't alike.
My favorite is that people get credit for updating based on evidence.
The more common reaction is for people to get criticized (by themselves and others) for not having known the truth sooner.