I hear what you're saying, but "Nationalism" and "National Socialism" are worth making a distinction over.
Every country and its citizens practice Nationalism. Have you ever worked with Hispanics? I have. They're some of the hardest working people you'll ever meet, and also some of the most proud of their country. They are incredibly proud of their flag and their culture. By and large, their culture is great, and honestly more right-wing than i think most people know; they take pride in the nuclear family, highly religious, certainly supportive of 2A, and view childbirth as a very sacred thing. So why aren't they vilified as Nazi's?
As far as the authoritarianism, until President Trump is trying to expand his power or diminish the power of Congress, that's simply a weak argument. Isn't the common criticism that Trump "didn't get anything done that he tried to?" You can't have both of those be true.
It's a pretty big elephant in the room to ignore Antifa/BLM riots and demands, then pretend "right-wing authoritarianism" is a legitimate threat because you saw some drunk guy do a Nazi salute once.
I don't agree on President Trump "loathing" free speech either. He's signed executive orders specifically to protect free speech, and we've never had a President whose speech has been criticized as heavily as his own.
Is he (or more accurately, his campaign) suing outlets like NYT and WaPo for libel and slander? Yes, but stating falsehoods as fact in order to generate an emotional response has been illegal for a pretty long time. Those same news publications are being taken to the cleaners by the Catholic High School kid for trying to ruin his life.
So I view this through what I call Maslow's Hierarchy of Political Needs. The top of that pyramid is the stuff you argue about in normal times. Marginal tax rates, how much a farm subsidy should be, bla bla. The boring stuff. If you're arguing about that, then your democracy is doing great.
At the bottom of the pyramid is your core values - the right to vote - free speech - the rule of law - etc. These are foundational. Forget for a second which side you're on and recognize that these are the things we're arguing over. Is free speech being suppressed? Are voting rights receding? Does POTUS respect the rule of law?
I'd argue that when you've reached that point, something unusually dangerous is afoot. Perhaps we'd agree on that premise, even if we disagree where the threat is coming from.
So with Trump, this is a walks and talks like a duck question. He fired Comey over the Russia investigation. He tried to fire Mueller (McGhan refused). He fired Sessions because Sessions did the ethical thing and recused himself. He's fired 5 IG's over the space of two months just this year. He's threatening to fire Wray, Esper, Haspel, and even voicing his displeasure with Barr.
The pattern is obvious. Trump demands loyalty to him personally above all else. That is hallmark authoritarian. A pure loyalists as Chief of Staff makes sense. But not at AG. Do you think he's "joking" when he publicly pressures Barr to investigate his rivals? What happens when there's a Micheal Cohen like AG that will do whatever the boss wants? Do you think that's what Trump wants at DOJ? I think he'd LOVE that.
Plenty of conservatives see this pattern too. Jeff Flake just endorsed Biden. Mike Fasano - Former GOP majority leader of Florida House - endorsed Biden.
They aren't endorsing Biden because they agree with his policies. They're endorsing Biden because they recognize how damaging Trump is to the country. They recognize that we need a stable foundation above all else, and Trump's presidency is fundamentally destabilizing.
Pro-Tip: If virtually every academic/historian type is already writing how damaging Trump's presidency has been, that's not going to change. Historians in 50 ye