It is questions like that that this blog are built around. Due to the progressives' complete dominance of academia(history) and media(journalism), I think it is safe to say that progressivism is the least understood ideology of modern history.
For what the article is and how it is set out to examine what it examines, I could not have written it this well. That simple, I could not even have come close. That's not to say it isn't without fault, for example, when I see someone quote Mill I immediately roll my eyes. However, my main goal is to highlight the origin of progressive history, which is conspicuously absent from the article.
In short, the origin of progressive history can be summed up into one single word: rejection. That is the origin of progressive hostility.
That's it. Rejection. Before being rejected, progressives loved and I mean LOVED America - at least, loved its government and what they could do with it. Read speeches from Woodrow Wilson or Theodore Roosevelt, there is no bitterness whatsoever to be found. Progressive ideology was at its height, they were open about being progressive, and nobody could stop them, and their tone reflects this.
That came to an end in the election of 1920. There is so, so much to learn from the election of 1920. The progressives were beaten so badly, that the only way progressives could become viable again is to put on a mask and usurp the word "Liberalism" as their new home. This happened by 1932.
Think about that. Who is your worst arch-nemesis? What if Rand Paul had to wear a mask of that guy - his next door neighbor who put him in the hospital, or if Steve Scalise had to wear a mask of James Hodgkinson? What if Mahmoud Ahmadinejad had to wear a Benjamin Netanyahu mask? What if Donald Trump had to wear a Hillary mask?
You get the idea. Your rejection is so complete that you had to look like the exact opposite, otherwise face extinction. Yeah, that would piss you off too. That's what the progressives have had to deal with since the 1930s. That is the origin of progressive hostility.
And to top it all off? The progressives first time in 90 something years that the they start to take their "liberal" masks off and start calling themselves progressive again, as represented by the Hillary campaign. And they lost again. To Donald Trump of all people! (Who in the progressives' minds, is the lowest of the low)
Yeah. You'd be hostile too. This must mean that you need to wear a mask again for yet another 90 years. Who WOULDN'T be pissed and hostile about that? This is why their pitch gets so much worse after 2016. It's 1920 all over again! I challenge anybody, ANYBODY, go read Wilson's or TR's speeches, read their books. You will not find any bitterness. Contrast that with the progressives of today, and the comparison could not be more stark.
There's a strong link between rejection, bitterness, and ultimately hostility. And this is their history. The progressives own it.