This wasn't "how to keep your shirt" - this was "how to keep your shirt if you have the resources to start your own fund. oh, and you'll basically be screwing your investors- so just don't tell them."
Lewis writes in a tongue-and-cheek style, but he's so deadpan, people think he's being serious.
Compare this article with "This is what happens when you lend money to poor people" (http://www.bloomberg.com/apps/news?pid=20601039&sid=a5lh...) , and the Hacker News reaction (http://news.ycombinator.com/item?id=50853).