Mr. Patterson really does a number on liberals in How to Be a Liberal. Seems that ignorance and hypocrisy are the two main requirements.
And he's probably right. So much of what today passes as progressive dogma has been demonstrated time and time again to bring more destruction than progress to the people under its influence.
Ignorance is an absolute must, but especially ignorance of three things: economics, human nature and all of recorded history.
One has to be truly economically illiterate to believe that high taxes encourages productivity, that union-imposed labor regulations don't dis-incentivize hiring, that energy regulations don't raise prices on the poor and working class.
Likewise, to be a liberal you must pretend that men and women are exactly alike in every respect and that communism produces the most happiness for the most people.
Of course you can search the history books in vain for a communist society that did not produce poverty, misery and/or death on vast scales. But American liberals don’t read history books – just note the vast throngs who came out to support Bernie Sanders for President of the United States.
My only complaint is the use of the word "liberal." It's more of a regret than a complaint. The word meant something entirely different a while ago, and it was a good thing. But lefties took over the word to label their own deeds with it, but they ruined it and are trying to abandon it. "Progressive" is another word from long ago that is having a revival. But if we agree that lefties don't know much about history then any old word will do. Hey, "Lefty" still works.