Since June 3, the Trump campaign has been running Facebook ads fearmongering about “antifa.” On June 17, the campaign added an inverted red triangle to some variations of the ad -- a symbol the Nazis used to designate political prisoners.

Using the Dewey Square Adwatch tool set to analyze Facebook Ad data, Media Matters found that the Trump campaign has run at least 2,110 advertisements with generic anti-antifa language since June 3. The ads ran on Facebook pages for President Donald Trump, Vice President Mike Pence, Team Trump, Black Voices for Trump, Brad Parscale, Latinos for Trump, and Women for Trump.
In recent days, the campaign has experimented with various illustrations in the post -- mostly variations of a generic alert image. All the ads have the disclaimer “Paid for by TRUMP MAKE AMERICA GREAT AGAIN COMMITTEE."

On June 17, the campaign ran 88 ads on the Facebook pages for Trump, Pence, and Team Trump with an inverted red triangle. The red triangle was used for political prisoners in Nazi concentration camps. The Trump campaign gave this explanation for the ad: This is an emoji. It's also a symbol widely used by Antifa. It was used in an ad about Antifa.

As one reporter noted, the inverted triangle is not a widely-used symbol for antifa.
Historian Jacob S. Eder, an expert on the subject, told The Washington Post that the ad is “a highly problematic use of a symbol that the Nazis used to identify their political enemies. ... It’s hard to imagine it’s done on purpose, because I’m not sure if the vast majority of Americans know or understand the sign, but it’s very, very careless to say the least.”
Facebook has previously let Trump run thousands of ads fearmongering about an immigrant “invasion,” even though the ads violated Facebook’s standards. Facebook also let the Trump campaign publish at least 529 ads with false claims of voter fraud.
The Trump campaign used anti-Semitic imagery in the previous election cycle as well. In 2016, Trump used a meme that featured the Star of David on a background of money to call Hillary Clinton the “most corrupt candidate ever.” Trump would eventually suggest that it was intended to be a sheriff’s star.
The 2016 campaign also did significant outreach to neo-Nazi figures. Campaign surrogates Diamond and Silk did an interview with a Holocaust denier. The Trump campaign gave press credentials to a white nationalist radio program, Donald Trump Jr. appeared on the program, and a Trump adviser gave interviews to that program at the Republican National Committee convention in Cleveland.