Blackwashing is one of the most basic forms of propaganda; it consists in damaging the reputation of inconvenient people/groups in order to prevent people from agreeing with them or supporting them.
Whenever someone (be it a single person or a group of people) says something that might damage the mainstream narrative's credibility and/or engages in something that might hinder the elites' agenda, this is countered by trying to find any kind of "dirt" about him or them; it might be something bad they did, or something wrong they said or some bad people he associates with; since almost everyone has some kind of skeleton in the closet, it is usually not hard to find something; once done, immediately reveal it to the world without even bothering checking the source credibility, and his/their reputation will be irredimably damaged and no one will take their side, even if their fault is completely unrelated to the original issue. If nothing relevant is found, even just mentioning minor compromising details might do the work.