"Democratic" and "Authoritarian" are extremely loaded here. The tankie line, that I believe, is that modern Marxist nations face ruthless ideological attacks from both without (imperialism, foreign influence, infiltration, demands to liberalize, war) and within (vestiges of the former bourgeoisie). Two schools of thought exist in how to go about implementing socialism: the friendly, open process that allows external and internal forces to collude and infiltrate and institute genocide, pain, and destitution (Sukarno's Indonesia, Allende's Chile, Revolutionary Catalonia, Iran, anywhere touched by Operation Condor...) and the more aggressive form of socialism that clamps down tightly on dissent and develops socialism with ideological protection and close management (Vietnam, Cuba, the USSR). Nations in the category of the former invariably see mass death, starvation, and the ultimate repurposing into a state managed by imperialist powers (Suharto, Pinochet, Hitler...). States in the latter category (verify this information for yourself, I don't want you taking what I say as gospel) invariably see world-best ascents in literacy, employment, public health, GDP, life expectancy, gender equality, income equality, and more.

This terrifies the imperialist powers. These actually existing socialism (AES) countries demonstrate an ability to thrive despite America's and the west's interests and attempts at destabilization. So what can be done? You lie about them. There is absolutely precedent for the US lying to its people about their enemies, in fact there is no precedent for the US not lying about their enemies. So us tankies decide that the truth exists somewhere between the US state line that Stalin is more evil than Hitler, and that the Soviet Union was a Utopian paradise. It is just as foolish to go with one side as it is the other. The only thing we know for sure is that the US has a long track record of genocide, torture, propaganda, imperialism, and lying about all of it, so why would we trust them?

So to sum it up, if I were to believe the line that reactionary insurrection is "Democratic" like the US state line says, and if I believe that AES states are "Authoritarian" and forcing policy on the people without consent like the US state line also says, then no, I don't support bringing in the tanks. I also believe it never really happens like that. I believe that AES countries make lots of mistakes, and I've never met a tankie who doesn't, but I believe that countries that are hard on reaction are better for it.

btw, thanks for engaging in good faith discourse. It's super hard on this topic and while I don't like your framing I recognize that it's not because you're trying to antagonize me, it's because you're faithfully portraying your beliefs.