It's sort of anti-advice.

He's giving an anecdote as an example of what-not-to-do. The moral of this anecdote is in the last line: "the best way to have a future is to be part of a team that values progress over politics, ideas over territory, and initiative over decorum."

Simple as that. Granted, he could have taken a less meandering path to that conclusion.

Regarding the conclusion itself, I couldn't agree more. I used to work for a company with a lot of internal politics and code-ownership, but now work for a more open company where progress is highly valued and no code is sacred, and the latter is vastly more capable at solving problems and creating great stuff.

I don't get what you don't get. The content of the advise was bad, but the overall effect of it on the author was good. It made him conscious of certain tendencies in the companies and allowed him to not be a purveyor of those tendencies.

He is saying that while he didn't take the advice, the giving of the advice changed him for the better; it changed the way he viewed his and other's code.

He's saying that it's important to remember that it is terrible advice.

When someone mucks around in your code, remember how shitty it is to be given that advice and try to handle the situation more gracefully.

When you are in a shop where that advice is considered good, find a way to leave.

I've gotta agree. I can't tell if he's saying to follow that shitty advice or not. I think he's saying, be part of a team where fixing things is more important than politics, but I have no earthly idea.