Earlier quoted context omitted.
Actually it has everything in common with the Nazis. The Nazis were the law-and-order party of their day. Very nearly everything they did was legal. That is why they documented everything so meticulously. They really believed they were the good guys. The main reason the Nazis are the iconic villains is not because what they did was that much worse than other atrocities that humans have committed through the ages, but…
Just because some villains started out being for law and order doesn't mean being for law and order makes you a villain. Being for law and order is the "we're the good people" disguise that villains hide in until they show themselves to be villains. But NOT being for law and order doesn't make you a "real good person". The correlation is probably strongly negative even.
That is certainly true, except for two things. First, the phrase "law and order" is a loaded term in American politics. (See https://en.wikipedia.org/wiki/Law_and_order_(politics) And second, Trump has made many xenophobic statements, both implicit and explicit. He called out Mexicans for being rapists. He called for a "total ban on Muslims entering the U.S." He failed to distance himself from endorsements by white supremacists. These things do not make Trump a Nazi, but they do make it fair to draw attention to the similarities.