In contemporary Germany, Hitler-comparisons are rarely taken lightly.
"Hitler comparisons are far less frequent in German public life than they are elsewhere in Europe, the US, or Israel," explained German historian Thomas Weber in an emailed response. Weber, a professor at the University of Aberdeen, has published numerous books on Hitler and Germany's Nazi-past.
"If you thus run a Google news search in German for 'Hitler comparisons Trump' almost all hits refer to articles that report for those comparison having been made in the US or elsewhere rather than in Germany," he said.
According to him, there are two reasons for Germans' reluctance to use Hitler comparisons. "For Germans Adolf Hitler is the symbol for all the crimes their country has committed," Weber wrote. "Nobody can ever be as evil as Hitler was," common thinking in the country goes. "Germans are worried that overemphasising Hitler (while discussing Trump) would appear as apologetic and distract from the responsibility of German elites and ordinary Germans for the crimes of the Third Reich."
Secondly, and consequently, Hitler comparisons are often viewed as the end of a serious factual conversation, and the beginning of an ideological mud-bath. Making such claims can easily turn into an embarrassment, especially for people in higher public office. In 2002, then-Justice secretary Herta Däubler-Gmelin was forced out of the German governmental Cabinet for comparing George W. Bush to Hitler over his plans to go to war in Iraq.
But in some cases, even Germans agree that Hitler comparisons are warranted.
In an interview conducted via Twitter, the author of the letter that went viral over the weekend defended his comparison on Sunday, saying exaggeration was necessary to raise attention in the United States.
"Of course it appears arrogant to claim to speak for the whole Germany. Of course it provokes ridicule if a German, of all people, says these things. That's fine. But I just had to say SOMETHING," explained the German author, who published his letter under a pseudonym and did not want to give his real name because he feared a negative impact on his business relations.
Born in 1972, the man said he was frequently asked during trips abroad why his grandparents had not prevented Hitler's rise to power. "When I travelled outside Germany in the past, I've often been asked how the German people could have fallen for Hitler back in the 30s and 40s. 'How could your people NOT have known?' they often asked. I don't get that question much lately,' " he wrote in a follow-up letter published on Twitter yesterday.
There is no doubt Germans feel uneasy about Donald Trump, to say the least. In a poll conducted in July, only 6.3 per cent of all Germans said they liked the idea of a Trump presidency. Many say they are shocked by Trump's remarks about immigrants, women and his determination to build a wall between the US and Mexico.
Weber emphasised that Germans widely perceived Trump as unelectable. "The near consensus indeed is that Trump is a minority-hating lout, who threatens to imprison his opponents, has disdain for democracy, and claims that he alone can fix everything."
Referring to the viral post over the weekend implying that the effects of a Trump presidency would come anywhere close to the repercussion of Hitler's rise to power, Weber expressed scepticism, however. "This is simply not a sentiment expressed as prominently in Germany as it is in the United States."
Other German historians have also been more cautious than their American counterparts to make Hitler comparisons. Speaking to Handelsblatt, a business newspaper, political scientist Klaus Schubert said: "Trump is an egomaniac in totally different circumstances".
According to Schubert, comparing the economic and political realities in the US with those in Germany's Weimar Republic which enabled Hitler to take over power leads nowhere.
Although his colleague Weber would not necessarily agree with Schubert's assertion that there are no similarities at all, Weber believes that such broader comparisons can have a dangerous effect.
"There is a 'crying wolf' danger of an inflationary use of Hitler comparisons, for instance that nobody will take Hitler comparisons seriously anymore when they really should and have to be made," Weber argued.
"The danger also is that people will rally to defend the people who unfairly have been compared to Hitler and feel sorry for them, rather than to figure out what's wrong with them."
