People have a right to be compensated for their effort. If you don't like it, no one forced you to tip him, and you got all that valueless writing for free. Had he charged up front, you either 1) wouldn't have paid, or 2) would have been disappointed with what you bought. Instead, he gave it away, and if you liked it he suggested a tip. No different than what I see on endless blogs on the net. If he hadn't "begged" for a tip, chances are he wouldn't have gotten any.
What gets me puzzled here though, is it seems that it's OK for a company to charge for something (that may even be valueless to many, many people) and it's expected, but if an individual person suggests tipping on their "product" everyone gets their panties in a bunch. He's viewed as weak for returning the money, and annoying for asking for a tip. Oh well, being reasonable isn't always popular.
If you don't want to tip, don't. But it doesn't make what he did any less noble.