No, he produced said shock as a marketing campaign, he admiited that.... it's just the way he's brandishing his form of righteousness - an INFP's righteousness would be more targetted and deliberate. John Doe got righteous on a bunch of disgusting strangers, but strangers nonetheless - pure Fe rage. I believe INFP's would only murder people they knew personally and KNEW, first hand, that they were evil. That's the personality of Fi.
I could be wrong though, i could see INFP i suppose. Passion was his modus operandi, we should draw his type with that in fact, no?
EDIT: now that i say it that way, i could see INTJ for John doe, too. Obsessive need for a well-ordered structured, and meaningful society.