See now this is a good point. I was thinking along similar lines, reading the article. Automatically thinking, "could this guy have handled this better?".
I want to make clear that I don't blame him, all he did was sell people live-typewritten short stories in the park. It's quirky, nothing that deserves Internet-wide ridicule (which happened because of the cropping of the photo, not the quirkiness per se). Also I don't think his clothes are that out of the ordinary, definitely on the "hipster" side as styles go, but many people wear this style, and indeed if you're buying clothes on a budget there's often not much choice: either you get something really shabby, or you have to pick one of the current youth main stream fashion styles. In that case I'd go with "hipster" too.
Anyway, what I thought was, if right that day when he hit Reddit's FP, he'd have made a simple webpage (could even be a Tumblr blog with one post in it) with roughly the first part of the story in this article--aka what he actually does and why he's doing it. Also, if he had one laying around, an uncropped picture of him with the typewriter and the sign.
The idea being, he explains that even in the Reddit thread (threads?) some people came to his defence. Giving them something easy to link to, makes that a lot easier. Especially if the topic comes up again on some other sub-reddit, the whole shaming-then-"oh wait he's just trying to make a buck, sorry" can be cut short if one of the first commenters just links to that page.
Basically what this does, is give you a communications medium back to your audience. Yes he now has an audience. That's how it goes in the 21st century sometimes.
Also write that URL tiny in the corner on the back of his paper. It's better than a Twitter account.