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.