We're going to judge you, not on the quality of your skills, but on whether you contribute to open source software or not.That's interesting. I don't see it that way, and neither do a lot of other people. Here's how I see it: Those people that do write code I can review provide me with more information than those that don't. They make my job easier. I judge the code, not whether the code is open source.
This is exactly the same phenomena as writing a readable resume, or blogging where I can read it. It increases their chances of being hired simply because they reduce the friction involved in the hiring process.
Now, does that mean that I will not hire someone who doesn't have a github account? No. It's my job to hire them too. But as an employer, it is remiss of me not to use all of the information available to judge hires. This is not prejudice, this is a business strategy.
Your words seem to indicate this is not a question of tactics and strategy. You introduce a lot of emotional rhetoric such as "political correctness." Frankly, I have NO idea what you are talking about, as Github has zero to do with whether one uses the word "bitch" in a presentation at a conference ;-)
I cannot read your mind, but in the conversation between you and I, YOU are the one introducing emotional baggage like "ideological prejudice," not me. I therefore suggest that if you want to stamp out all this zeal and prejudice, you start with YOURSELF. I am not the one claiming that people who write things I can read are or aren't better than those who don't. I am not the one with an axe to grind. I am simply a fellow trying to get my job done and looking for efficient and effective strategies for doing so.