Demagoguery is poorly reasoned, emotively strong political language, especially slurs. The word demagogue is a slur, so those calling others the D word contradict and condemn themselves.
When the name Huey Long pops up, so does the slur demagogue. The frequency of the correlation indicates that demonizing Long as a demagogue is part of the establishment narrative. We should be skeptical of ruling group narratives because ruling group narratives are almost always poorly reasoned, designed to make horrific ideas pass as "centrism."
I read Long's much reviled speech, a speech made with no teleprompters or focus groups. Long's speech contains only one slur, the mild ad hominem "financial barons." Long's speech does contain numerous fallacious claims. It is not my point here to pick on all of Long's bad ideas. But the speech barely consists of demagoguery.
Contrast that speech with today's ruling group opinion makers when they write on ethnoracial issues. Their writings are packed with multitudes of super slurs "racist," "far right," "Islamopbobe," "bigot," "libtard," "right wing." Yet the ruling classes imagine that they are ethical and tolerant, almost never get fired or even criticized for spewing antiwhite super slurs. I have never heard of our rulers calling each other the D word.
Their heads would probably explode before they could write 3000 slur free words on ethnoracial issues.
Outright supporters of Marxism, self-described activists, are treated as somewhat mainstream, as if it were some accident that millions died and billions suffer from Marxisms, including multiculturalism.
The D word is usually reserved for ethnoracial fact facers or those labeled as economic populists, those who support capitalism but not crooked capitalism. To put it bluntly, you a more likely to be labeled with the D word for telling the truth to the ruling groups than for fallacious claims.