The thing about the original oompah lumpa thing or however you spell it... It doesn't mean he thought those things were good things or approved of them. Authors don't personally approve of or think every action or every thing in the stories they write are good things, do they. I think Charlie and the Chocolate Factory/Willie Wonka is/was supposed to be dark in all sorts of ways, like several of his other great books. Maybe it was even supposed to be a criticism of racism, slavery etc.
I think it's very bizarre and wrong that people are calling him sexist too if it's based on characters or something in his fiction books. I don't know what leads them to think that tbh, I don't know anything about his personal life if that's the reason why.
If there is something racist or sexist or something racist or sexist happens in a fiction book, some people really think this means the author is racist/sexist? What about other bad things that happen in fiction books? What if there are murders, rape or child abuse? What do you think of authors who constantly write stories about murders? What do you think of whoever writes certain tv shows/films that have dark/bad things in them?
As for considering their personal life, I don't know how far you should go. It's personal choice how one reacts to the information. Considering how many creatives, scientists etc had terrible views and actions, there might not be much left if you cancel everyone and their work. I don't know how many people pre-2019 would survive considering every day is getting stricter and stricter and something new that is offensive. Yes Roald Dahl was apparently antisemitic if those quotes are accurate. It's individual choice how one reacts to that information, and if someone still wants to read his books/give them to their children that doesn't make them antisemitic or approving of antisemitism. What tv etc should do about showing/celebrating his work, I don't know. They should educate people about this antisemitism. Showing his work... well, that can be looked at as separate from the personal life. There's plenty work that would disappear if we were going to examine everyone for what is unacceptable today, especially those from decades ago.