In one of the controversies discussed in the article, Facebook banned an ad on the grounds that an upside-down red triangle constitutes hate speech - it's "a triangle symbol used by Nazis to identify political prisoners", you see. So I'm not sure the concept is quite as well-defined as you're suggesting.
Except that is defined, that's a thing that's real, and the upside down red triangle specifically was used to identify political prisoners of the Nazi party, like liberals, socialists, and unionized laborers.[1]
I guess I'm not sure of your point, because to me, the use of the symbol, in a political context, and especially in the context of a polemic populist political campaign, is problematic, regardless of whether or not the Trump campaign or whoever backed that advertisement knew what it was.
The question isn't whether it's problematic in some generic sense, but whether it's hate speech or a call to violence. I'm extraordinarily skeptical that anyone sees a red triangle and thinks "ah, I understand, the triangle is telling me I should go engage in political violence".
