I don't really see it as ignoring him, really; more ignoring the content of what he posts.
The more you poke sticks at Duke in that fashion, the more you strengthen his resolve to continue posting what he posts. And even if you left him alone, he'd still posts what he posts. You can't change his ideology any more that he can change yours.
I suppose I've been around him long enough to have gotten used to it, even though I still find his obsession with a single subject -- and the extent he's embraced partisan politics -- a bit frightening.