9 years before Hitler became president of Germany, he wrote in Mein Kampf: "the personification of the devil as the symbol of all evil assumes the living shape of the Jew." and "Aryans were, and are, alone “the carrier of the development of human culture."
He foreshadowed the Holocaust by saying "that the ‘sacrifice of millions at the front’ would have been prevented if ‘twelve or fifteen thousand of these Hebrew corrupters of the people had been held under poison gas."
12 years later, he killed (among others) over 15 million Jews, gays, Russian civilians, and Roma people.
Trump on the other hand, has said "“total and complete shutdown of Muslims entering the United States until our country's representatives can figure out what is going on.” He also said "And by the way, many, many, most Muslims are wonderful people."
I challenge you to find a quote of Hitler saying something this nice about Jews.
No doubt the Holocaust was one of the most horrific crimes ever committed -- should we not then be all the more vigilant in preventing such similar hate speech from entering the mainstream?
I would say a more apt comparison to Hitler is the language used in the parent to my comment: "If that's the man Thiel wants to stand with so be it. But I won't forget." An implied long-term threat against someone for voicing political support for the Republican candidate for President of the United States. Now that is a tactic straight out of the Joseph Goebbels playbook.
Hitler:
Before he even gained power, he said he wanted to gas the devil jews. Before he won power democratically, he tried to seize power in a violent coup that left 15 people dead.
Once he gained power, he quickly imposed a series of laws that made it illegal for jews to work in academia, own property, work as judges, work as doctors, etc.
Trump:
Enforce immigration laws that are already on the books, provide extra scrutiny to Muslims ("most of whom are wonderful people") before they are allowed into the country.