"Don't like it, don't read it" is a cop-out. He's not immune to criticism from those who dislike him or his work. Nobody is.
constructive criticism, sure. did you see the raging hate-on some people have for tim buckley of ctrl-alt-del or jeph jacques of questionable content? saying tatsuya ishida should roll back the apologetic attitude about his past work because it's layered on too thick and it costs his comic its cheery humor is constructive. calling jacques an idiot because he cut his drawing hand and he should never have healed is ad-hominem criticism and is not ok in my book.
at least that is my viewpoint. i try and hold views to the work, not to the person, and if the person makes the comic not to my taste anymore, i'll try and explain it before stopping reading the thing. artists progress faster when you give criticism for the reason you don't like it anymore, and they'll just get bitter if it boils down to "u fag lol go kill urself". you'll also lose credibility, or worse, sound like a middle-schooler on the web.