I'm only surprised that Hergé still used stereotypes about Jews in "The shooting star", when he was such a pioneer about the Chinese several years earlier in "Blue lotus". But I guess you're right, that he was forced to satisfy his Nazist bosses at the time.
Amongst Roman Catholics and other Christians it was not uncommon to have prejudices against Jewish people at that time. The Holocaust may have changed this later. I suppose: also for Hergé, who was quite a sensible man. Later he might have felt ashamed for Blumenstein/Bohlwinkel but maybe more ashamed for a bit opportunistic behaviour during the occupation, like the majority of the people.
Still I find remarkable other tendencies in the Crab and the Shooting Star that could be used for Hergé's defence:
Haddock and Allan seem to be adversaries when Tintin meets them, but a short while later Haddock is Tintin's helper. This could be a metaphor suggested by Hergé: "The English are supposed to be our enemies, that is what the reigning occupying power lets us believe, but in the end the English will help you!" Captain Chester is also an Englishman who helps Tintin and Haddock in the next album. Are these signs of hidden resistance and sympathy for the Allies? By their introduction the censors of Le Soir are satisfied: Allan an Haddock are villains and drunks, but when they don't look sharply anymore, one of these two turns out to be Tintin's best friend.