Earlier quoted context omitted.
The "for Hackers" angle is in the fact that most hackers (and I admit I'm generalizing here) don't lift weights regularly. He's basically saying, "if you have written off weightlifting because you think it's just about vanity or because the gym is full of asshole jocks, you might want to reconsider because it can actually help your confidence in business, help you to solve problems, and isn't that hard to get into af…
I think it's mostly a gimmick to make this article popular on sites like HN. In a similar vein, stay tuned for my next two articles "Making a sandwich for Hackers" and "Cleaning your bathroom for Hackers".
To reiterate my point, making sandwiches and cleaning bathrooms is something most hackers do regularly. Lifting weights is not. A better analogy would be a "learning calligraphy for hackers" article that explained how learning calligraphy can be a benefit to hackers and how, given hacker's programming knowledge, one should go about it.