Just a very long explanation that is summarized at the very end of the piece which is:
“P.S. For any non-typographers who made it all the way through this article, if you want to double-space, do it. If you want to single-space, fine. Just please don’t try to enforce your view on the world. Stop judging people. Because, really, if you’re not a typographer, chances are the stuff you’re producing in MS Word or whatever has dozens of other worse spacing sins than double-spacing your sentences.”
I read through the whole article so you don’t have to!