Several comedians, world leaders and political activists have compared Donald Trump to Adolf Hitler recently. (Peter Stevenson/The Washington Post)

If there’s one comparison you never make, it’s comparing someone to Adolph Hitler. It just isn’t done, because almost no one in history was as bad as Hitler was.

But in an election season that has broken a lot of the boundaries that used to dictate what could and couldn’t be said in presidential politics, that particular trope just won’t go away.

Louis C.K. and "Saturday Night Live" both went there this weekend when it comes to Donald Trump and Hitler. But they were hardly the first. In fact, it's party of a growing chorus, mostly coming from celebrities.

Trump had already been drawing comparisons to Hitler and had to defend himself after failing to disavow former Ku Klux Klan leader David Duke. Current Mexican President Enrique Peña Nieto and former president Vicente Fox both made the Hitler comparison. Then, on Friday, Bill Maher called Trump's rallies "Hitler-y" during an episode of his HBO show, as a montage of rough treatment of protesters at Trump rallies played onscreen.

Louis C.K. joined in Saturday, just hours before the Trump rally in question. He posted a 1,400-word rant about Trump at the end of a letter to fans about his new television show, "Horace and Pete," in which he called the Republican presidential front-runner "an insane bigot" and urged voters to cast their ballots for any other candidate.

And some even saw a Nazi comparison at a Trump rally later on Saturday in Orlando. Abe Foxman, former national director of the Anti-Defamation League, took issue with Trump asking his supporters to raise their right hands and swear to vote for him.

"As a Jew who survived the Holocaust, to see an audience of thousands of people raising their hands in what looks like the ‘Heil Hitler’ salute is about as offensive, obnoxious and disgusting as anything I thought I would ever witness in the United States of America,” Foxman said.

Then, in a somewhat remarkable piece of timing, "Saturday Night Live" ran a fake advertisement Saturday night purporting to be funded by "Racists for Trump." It also, in its cold open, featured Darrell Hammond-as-Trump talking about how people haven't seen a campaign like his since Germany in the 1930s.

The question it begs is: Does this really hurt Trump? The idea of celebrities comparing their candidate of choice to Hitler and calling him racist probably furthers the idea that he's an outsider that liberals and the political establishment are afraid of. Basically nobody who has attacked Trump so far has actually knocked him down; why should this be any different?

From saying, "I'm not a political comedian," in 2011 to begging fans to not vote for Donald Trump in early 2016, Louis C.K. has subtly evolved in his political comedy over time. (Nicki DeMarco/The Washington Post)

Trump has repeatedly said over the course of his campaign that he "(gets) along with everyone" and that everyone likes him. At a rally Saturday, he touted his ability to unite people.

"There has never been a greater division, just about, than what we have right now – the hatred, the animosity," he said. "I will bring people together. I'm going to bring people together, you watch."

Clearly, some haven't gotten the message.

Update:

Trump responded to the critiques on the Today Show on Tuesday, calling the comparison to Nazi imagery "ridiculous."

"Honestly, until this phone call, I didn't realize it was a problem," he said. "If it's offensive, if there's anything wrong with it, I wouldn't do it," he said.