How did he get so popular in the first place? I have to admit I’ve never read one of his books myself, but I know my kids enjoyed some of them. Surely that’s the key - he got / gets kids reading? He may not be a literary genius, but kids respond to his stories.
As others have said, many many authors and artists were / are less than perfect human beings. I absolutely loved Enid Blyton as a young child and although I can see her writing is riddled with unpleasant stereotypes now, she ignited my love of reading. It’s strange she wrote lovely warm stories about idealised families as she was apparently a terrible mum to her own kids - emotionally cold and very controlling (after her divorce, she stopped her kids from seeing their father and barely had time for them herself).
Dahl was very cruel to his wife, Dickens was a monster to his, Virginia Woolf - a feminist icon - was openly anti-semitic and horribly elitist in her diaries, Picasso was really awful to his wives & so was Hemingway, JD Salinger (Catcher in the Rye) had relationships with teenage girls, Caravaggio was a violent criminal and murderer! Are we going to bin them all?
Like I say, perhaps Walliams isn’t a genius writer and is certainly a flawed human being - but there must be something kids respond to? Like Blyton?
God knows, we need to get kids reading… so if you don’t want the books, take them to a charity shop and let people choose for themselves.