“The social media site has deleted pics of artworks by people like Kate Durbin and Erika Ordosgoitto. It has blocked users like Frédéric Durand-Baïssas for sharing paintings including Gustave Courbet’s ‘L’Origine du Monde.’ And though some people have protested by creating Facebook groups like Artists Against Art Censorship, recording every instance of censorship — let alone fighting back — is next to impossible.”