I mean he just tweets about bitcoin so often. He may be thinking that he is guiding his followers out of bitcoin but what he could be doing is making them more curious that they will eventually buy like his son did. Bad publicity is still publicity eh?
Its not always like this - if you're talking shit over small service/technology/company/etc its going to hurt them badly.
But if they're big enough - it works exactly as you put it "Bad publicity is still publicity"