I learned about the different badges that Nazis gave people before murdering them in seventh grade.
I've been to Israel twice, including to Yad Vashem. They have a section on non-Jewish victims as well. It's obviously not the focus but as a gay man myself, I remember seeing the pink triangle there. Granted I was 19 when I went so not a kid and I already knew what it was and what to look for. Perhaps a child would not yet be taught about the triangle and so wouldnt even have noticed. Certainly when I was 12 I was not taught this. But that was almost 30 years ago. Perhaps these days they do teach that.
He claimed to be an expert, not a literal expert, but he claimed to be an authority on that matter.
Then several people pointed out that it was well known to them even though they did not have his life experience. Shrug the exchange demonstrates no single person can be the capital A authority on things like racism and so on.