In the early 20th century the wealthy sent their kids to Europe to college. Those kids came back being fully indoctrinated with Marxist idealogy. Marxism was new and there weren't a whole lot of countries who had implemented it. The news coming out of the Soviet Union was all good until 1928.
Hitler was New on the scene and American Progressives looked at Hitler's ideas and saw that they were mostly in line with Marx. The same with Stalin and Mussolini.
Those 3 tyrants were very popular among the Progressive left. The famous songwriter of that time, Cole Porter, included the lyrics, "You're the top, you're Mussolini" in his song, "You're the top".
He later took it out when news started coming in of just how awful both Hitler and Stalin were. Mussolini wasn't as murder happy as Hitler and Stalin were but he wasn't much better than either.
Finally when WWII happened the Progressive movement lost a huge amount of steam. People dumped it as fast as they could. There was still a small augment that held out hope that socialism and communism were great ideas. Socialism is the prequel to communism.
But those same people, who made their way into academia, pushed Nazism and fascism off as right wing idea.
The left has previously confiscated the word "liberal" to hide behind. Liberalism used to be all about liberty, freedom and inalienable rights. It was a very pro-constitution philosophy. Then the Marxists stole it and made it all about "freedom" through massive and controlling governments.
The right, who still very firmly believed in freedom, inalienable rights and the Constitution, were all of the sudden being accused of being Nazis and fascists. That has been perpetuated until today.
The fact of that matter is that the right has NEVER been associated with those evil socialist regimes. We have always deplored Nazism, fascism, communism and socialism. Those are foreign ideas that rob the individual of all of their inalienable rights. It is the polar opposite of what our founding fathers gave us.
So, yes. It was the Democrats who brought Neo-Nazis to America. It was the Democrats who created the KKK. It was the Democrats in the South who wanted to form their own nation. Abraham Lincoln was the first Republican president and he ran on the party platform of abolishing slavery. The Dems were very pro-slavery.
This is all historical fact that can be easily verified if you are intellectually honest and try to find the original sources.