"The media has been her number one surrogate in this. Without the media, this wouldn't even be a contest. But the media has built her up. They've let her slide on every indiscrepancy, on every lie, on every DNC game trying to get Bernie Sanders out of the thing," Trump Jr. told Philadelphia-based conservative talk radio host Chris Stigall on Wednesday.
"I mean, if Republicans were doing that, they'd be warming up the gas chamber right now. It's a very different system -- there's nothing fair about it," Trump Jr. added.
Trump Jr. also said that as a Republican running as an outsider, "every day, everyone's throwing everything they could possibly throw at him."
Gas chambers were used by Nazis in the Holocaust -- the genocide of 6 million Jews and millions of others during World War II.
Trump's campaign denied that Trump Jr. was referring to the Holocaust, saying he meant the "gas chamber" used in capital punishment.
"The liberal, dishonest media is so quick to attack one of the Trumps that they never let the truth get in the way of a good smear," Trump senior communications adviser Jason Miller said in an emailed statement. "Don Jr. was clearly referring to capital punishment to make the case that the media continues to take words out of context in order to serve as the propaganda arm of the Hillary Clinton campaign -- something that's only gotten worse as Trump's poll numbers have improved."
Evan McMullin, an independent presidential candidate running as a conservative alternative to Trump, lambasted Trump Jr.'s remark on Twitter, saying, "An unsurprising Nazi reference from the 'alt-right' movement's presidential campaign. This is the real Trump."
The Anti-Defamation League, a prominent Jewish advocacy organization, on Twitter called on Trump Jr. to apologize.
"Trivialization of the Holocaust and gas chambers is NEVER okay," the group said in one tweet, directed at Trump Jr.
"We hope you understand the sensitivity and hurt of making Holocaust jokes. We hope you retract," it followed up in another.
Hillary Clinton for America chairman John Podesta called the comments "insensitive."
"It's factually inaccurate, but the particular wording is extremely insensitive, divisive and probably pretty consistent with the type of rhetoric he heard around the house growing up. I think it is never acceptable to use language like that," Podesta said during a press call.
Trump Jr.'s comments came after he in another interview dropped his father's campaign's argument that he hasn't released his tax returns because of ongoing IRS audits -- instead saying those returns would distract from his father's message.
"Because he's got a 12,000-page tax return that would create ... financial auditors out of every person in the country asking questions that would detract from (his father's) main message," Trump, Jr. told the Tribune-Review in Pennsylvania
in a piece published Wednesday.