Once people realize that there are only ten people on television telling them "The capitol building just survived the deadliest terrorist attack in American history started by the bad orange man!" and that the vast majority of people actually support Trump their narrative falls apart. They just can't have that.
I'm kind of on the fence about this. How exactly would agent provocateurs take advantage of this? Everyone would be marching with their weapons, what are they going to do? Are they going to just start shooting innocent civilians? Sounds like a pretty good way to end with a lot of dead glowies. About the only thing they could do is come with a large enough group to not instantly get ventilated, but then they give themselves away: "Small group of white supremacists Trump supporters opens fire in million man MAGA march before being summarily executed by their fellow white supremacists in ritual homicide!"