This is not a logical analogy but rather an appeal to emotion.

If someone had jumped Graham in the street and beaten him with a bat and David was condoning it using the argument that Graham considered his art to be effective so was "asking for it" then the analogy would hold; he's not, he's merely stating his viewpoint on the nature of Graham's presented views.

People are welcome to assert whatever they like, including that anothers assertions are a load of rubbish.

One should be prepared to justify/support/defend their opinions or should consider keeping them to themselves if responses upset them.