1) Reagan wins in 1976 = Reagan loses in 1980. It's pretty damned hard to beat an incumbent, and Reagan was running a damned good campaign, knew how to play media, and simply connected with people better.
2) Democrats are kind at heart and want to do the right thing, while the Republicans are at best socio-paths anxiously waiting to snuggle up to literal Fascists (something that had no party distinction in Washington) or are outright would-be Fascists themselves. Don't get me started on the wish-fulfillment TLs where the author just goes "I have a Republican as President, so what would be the stupidest thing to do?", regardless of whether or not a Republican would ever practice that position. Thus, Republicans are simultaneously anarcho-Capitalists, Westboro Baptists and the Stanford Prison guards writ large.
3) That minor Communist regimes were "decent". To put this in perspective, Pinochet is a by-word for horrendous actions by Right-wing dictators. How many people died under his coup and slaughter of Chilean democracy? 3000 (3000 too many). How many did Tito, a guy who gets a bizarre amount of respect kill? The median estimate is 100-250k. So even the minor Communist dictatorships were not vanilla authoritarian regimes; they were seriously violent.
4) South Vietnam is just irredeemably corrupt and destined to fall because its a Right wing authoritarian dictatorship in Asia. Somehow, South Korea and Taiwan avoided this fate.
5) My biggest: World War 2 is Black Vs White morality, while the Cold War is grey morality. On the allied side in WW2, the two biggest mass murderers in history on raw numbers (Stalin and Mao) were present, not to mention Chiang, the Latin American dictatorships, Colonial Britain and France and Jim Crow America; there was even a democracy in Finland fighting for the Axis. Yet, somehow, when even the worst regimes on the West's side in the Cold War didn't have a body count reaching over one or two million, and the West are fighting for global influence against the single most destructive ideology ever practised on Earth (in raw numbers) it's considered a grey morality zone. The fact that the Soviets treated Ukrainians horribly and the Ukrainians wanted them out does not make the Nazis any better, so why do the various revolts against despicable Latin American dictators mean that there was some righteousness to the Soviets?