You seem to have changed what he said into a bizarre absolute. The point of Derek's post is that many of us unnecessarily keep many things secret for no rational reason at all. He's just suggesting that we ask ourselves, "Why is this secret?" Because a lot of the time, we're just needlessly building paper walls around our insecurities rather than keeping important secrets.
And given that Derek has code licensed under MIT, your conclusion that he was unaware of that license is obviously incorrect.
Yet that is the conclusion he comes to.
The other possible conclusion, as I noted, is that he has previously been unaware of Free/Open Source and Creative Commons based licenses. In which case he needs not talk on secrets but rather on licensing.