Just to add:
Changing Miss Trunchbull's description from "a formidable female" misses the point - Dahl is using alliteration, which we teach children in KS2 to make their stories more readable/less boring to read. Children know what a female is. If we remove or bastardise literary devices such as this - the story becomes less readable.
Part of Dahl (and Walliam)'s appeal to children is to write about the revolting. Sanitise the writing by eg swapping gendered language, and many children just won't read them any more. These authors often use the revolting/unfair to prompt feelings of justice and fairness in the reader.
If we are to remove all 'problematic' elements in a story, where will it stop? In 30/40/50 years time will we see thrillers remove all descriptive language? Will Malorie Blackman's excellent, thought-provoking descriptions be altered and watered-down?
If an author has a character express views we vehemently disagree with, should they be replaced?
Again, where does it stop? We already see a move from policing fiction, to challenging factual writing. Scientific writing is already changing, to the detriment of clarity.