I'm not sure I agree that polarization happens best if people are free to air their views. Something else might happen instead: discussion. (Free) discussion and debate in my opinion decrease extremist views because people feel like they can say what they think and they can work out their views in discourse (which really is part of building views, people learn from conversations and even from debates). If the climate is too dangerous for people to speak, that's when internal anger builds that has little outlet until of course someone like Trump comes along to encourage the unleashing of that rage, which he can play like a snake charmer.
I'm not sure how much you need. For instance would you agree already from the content of his Tweets and what he says in his rallies (which btw are ONLY for his supporters and not all Americans) is decisive by drawing on people's fear, anger and hatred, and calling out enemies to hatefully chant against whether they are immigrants or muslims or the libs in general or whichever group he wishes to declare the enemy today. The energy that gets fired up is hateful against other people in the same nation.
Then there are the violent outcomes of Trump's rhetoric. This article has a list of some examples:
https://abcnews.go.com/amp/Politics/...ry?id=58912889
What will be the reaction from the left to this kind of thing? Will they possibly become increasingly less "woke" in response to an increasingly violent right wing that is actually now easy to link directly to racism and hate crimes? Of course not. This will tell the left it needs to double down hard, it needs to become more extreme to fight the extremism. It needs to burn cities and destroy things if need be. It needs to make sure no one is allowed in its society who displays any view that does not meet a standard of moral purity. It needs to grow its dogma to become strong.
And when it does, Trump likely rejoices, because then he can tell his followers, "see how extreme the left is" and basically paint them as enemies in a holy war. And they will agree with him when he starts turning Homeland Security into the secret police, able to detain people whenever they want. Naturally like both sides blind in the political divide they don't see how that threatens their freedom as well were a left-wing extremist to get into office (how now the set up is already there for them to do one of the worst things in nations ruled by dictators--make people disappear because of their political views). Likewise, the political left doesn't see how their interest in increasing censorship creates pathways to censor their own side for extremism. If the social media giants increasingly censor political speech they can also censor eventually progressives rising in politics who rely heavily on social media to promote themselves. It gives the social media giants too much power over politics. But naturally no one notices the threat as long as it's only working against the other side.
Trump didn't start all the division, but he used it to win an election and he'll use it again. The closer we get to Nov. the more he seems to focus on the culture war. And surely I am not the only one who noticed how after Trump's election extremism in the US seems to be at an all time high. Who is fanning those flames in every speech and tweet? Could it be the leader of the nation?
PS. Trump on cancel culture:
https://amp.cnn.com/cnn/2020/07/07/p...ngs/index.html
Some of these examples are about boycotting corporations, however that's kind of part of this too. Corporations are reacting to the political division just as everything is. It affects who they hire, who they fire, what they say and promote, where they put their money, what their culture initiatives are, etc. And that affects all of us, it affects what we can say and do without economic penalty.
Also many examples are just about if someone said something that he personally doesn't like, because he is a mini-dictator with fragile ego.
But basically he plays the same game as the left while saying he's against the game. His side won't notice how this is pervasive on their side as well, and of course they can always just see it as necessary: you have to control these left wing extremists so they can't take over (you have to control people).
CNN btw as far as I know has never really called out cancel culture on the left. It's left-leaning and blind to its own side's failings.
This vid does a nice summary theory of how Trump plays. He's good at division. He knows how to play division in his favor:
https://youtu.be/AkYnMDKVwoY
Like he doesn't say divisive things for nothing. Every time he's doing it he's doing it on purpose for his own ends.
If Trump were against the division because it threatens the integrity of the entire nation he would attempt to unify the entire nation. Can you really say a president who has declared the other half of the political spectrum (the entire left-leaning half of the nation, over 100 million people) the enemy, does not wish for division, strife and chaos? The very simple fact that his rallies are only for Republicans, that Republicans are the ONLY Americans he represents, says a great deal all on its own.