the obvious evidence that propaganda persuades no one

 Is the Fox News watcher persuaded by what the NYTimes says? Not at all. Whatever the NYT presents only confirms the Fox watcher's beliefs about the NYT's bias. Is the NYT's reader persuaded by Fox News? Nope. Propaganda serves to confirm the beliefs that its audience already believes or wants to believe. Propaganda does not persuade. Far from it: it confirms the negative judgments about the out-group. Propaganda serves to confirm one's conviction that the out-group is morally and informationally defective and dangerous.  

Two facts emerge: propaganda doesn't persuade, and political polarization belies the post modernist and the Marxist assumption that the culture has a single discourse of power. There's no systemic belief structure directing all minds. Liberal democracy has a structure of mutually out-grouping, with the in-group significantly determined by accepting anything the out-group rejects, all the while developing and innovating means of rejecting the Other. 

In this innovation the Right has been particularly fecund. It used to be the conservatives who were stuck in the mud of the past. Now the Right is full of reinvention of natioalisms and conspiracy theories, while the Left is stuck with its Enlightenment principles and its self-righteous moral superiority and censoriousness. 

important addendum: if you spend time with Fox watchers you'll see that they find Fox fun. The NYTimes science features are more engaging to me, but I'm what the Fox watcher would call "boring". Have you noticed that the Right inspires its audience? Whatever you think of Adolf, his ideas, his imagery, his wingnut megalomania -- it's all inspiring, exciting, appallingly exciting, frighteningly exciting, like a drug high. Truth and moral virtue -- are these inspiring or are they chastising, limiting, oppressive? What did Gilovich say about confirmation bias, "can I believe this" is a call to inspiration and imagination, like conspiracy theories wild as far as eye can reach; while truth says "you must believe this", a shackle, a constraint on freedom, an indignity, a violation of human expression, individuality and unique path of life. People love Fuentes and Alex Jones enthusiastically. Does any love Ezra Klein? Enthusiastically? 

I remember the Left when it was celebratory, like the early years of the gay rights movement, rioting and bashing cops. Now it's become marriage. The Left is no longer tied to counterculture, preferring mainstreaming itself as a normie. The new counterculture is nationalism. 

Well, I'm waiting for the Left and Right to unite against the Evil Empire's alliance with Israel. Maybe that will be the new common ground of countercultural protest.