The president's message sowed fear over the rise of antiracist protests, warned of so-called "Dangerous MOBS of far-left groups", and claimed without evidence that antifa (shorthand for anti-fascists) is "DESTROYING our cities and rioting".
Update 12:34pm CT, June 18: Following publication, a Facebook spokesperson informed the Daily Dot that the company had taken the ad down.
Trump's campaign has responded to criticism over its use of the triangle by attempting to link it to anti-fascism; the campaign told the Washington Post, "The red triangle is an antifasymbol".
He also said there had been someantifa who had used the red triangle, but that it was not a common symbol used by the group.
"Jonathan Greenblatt, chief executive of the Anti-Defamation League, said the president's campaign "needs to learn its history, as ignorance is no excuse for using Nazi-related symbols". Although certain symbols the Nazis deployed have been reclaimed, including the pink triangle used in concentration camps to label homosexual inmates, the red triangle has not been recast in a similar way, said Jacob S. Eder, a historian of modern Germany at the Barenboim-Said Akademie in Berlin.
Facebook has taken down an ad from the Trump campaign that went after antifa and leftist groups with a prominent display of an inverted red triangle in a black outline, a symbol the Nazis used for political dissenters.
"Nazis Put This Symbol on Political Opponents' Arms".
Facebook's ad library shows that the ads, paid for by the Trump campaign's fundraising committee, first started running on the platform on Wednesday. Two other ads - which use the same wording but don't include the photo of the red triangle - remain active on Facebook.
While admittedly not the most recognizable Antifa symbol, the red triangle can be found in connection to the movement on several websites, and in 'Antifa: The Antifascist Handbook.' The author Mark Bray acknowledges that Antifa was directly influenced by European antifascist groups that reclaimed the "red triangle" and utilized it.
Trump announced earlier this month he planned to designate antifa a terrorist organization.
Facebook is under pressure to clamp down on political misinformation following failures to block foreign influence campaigns in the 2016 United States election, while at the same time remaining an open platform for election debate. CEO Mark Zuckerberg has consistently defended Facebook's decision to keep Trump's controversial posts, citing free speech.