Of course it is right to knock newspapers; as Noel Coward said in another context, they should be beaten regularly, like gongs. And newspapers tend to be identified with typical readers:- The Sun and white van man, The Torygraph and retired colonels in Cheltenham, The Grauniad and teachers, etc. So to knock any newspaper may be seen to knock its perceived typical readership, who may or may not take offence, but that should not stop the knocking. After all, we all know that people buy newspapers for all sorts of reasons, not just because they identify with a particular rag's politics.