Facebook/Meta itself seems to disagree with you - the very article we're discussing says the accounts were reinstated after inquiries from the author of the article, and a Meta company spokesperson said the accounts were "incorrectly removed".
Many uses of Hitler on Facebook would violate their rules against hate speech, so I'm not surprised they have automation looking for that name. But even Facebook now agrees that a play about a real person who was forced to taste Hitler's food before he ate it is not such a violation.
