This is the first I’ve heard of it, but here’s one of his infamous quotes:
"There is a trait in the Jewish character that does provoke animosity, maybe it’s a kind of lack of generosity towards non-Jews.
I mean, there’s always a reason why anti-anything crops up anywhere; even a stinker like Hitler didn’t just pick on them for no reason.”
His other quotes tend to be condemnation about specifically Israeli zionism and barbaric murder, but i don’t have context as to whether he’s referring to palestine or not. Some people might have more sympathy for these statements these days, but a lot of his other quotes have to do with Jews controlling money and media, less defensible prejudice.
Avoid blaming others for your own misreading of the quote.
You can try Merriam-Webster/Oxford/Cambridge to suggest your own exclusively non-race related definition of racism.
You can similarly try contacting the museum to see if they’ll change their statement regarding their condemnation of Dahl’s racism.
Keep us updated on your efforts.