I don't think you are wrong on the idea they'd try this, if for some reason they were stupid enough to, but your implication it would work and do anything but enrage the right further is... wrong.
Within an hour they'd find evidence the "right winger" was an actor, glowy, or lefty-turned-righty (magically just in time for the event). It wouldn't matter if the evidence was real, it would be
real enough, and no amount of smug CNN thinkpieces or desperate attempts by Fox News to get us to believe CNN
just this once would stop it. They'd try to ban discussion of it on social media, which would just cause the Streisand effect. Everyone would "know." "They" killed him and tried to frame "us."
Then you'd have some kangaroo court "investigation" which would be rammed through without anyone to the right of the Turtle being allowed to speak or participate. I could see Schiff being involved again, because why the fuck not, he seems to like showing up being a smug little prick and
doctoring evidence, and he'd absolutely do it this time too, taking fake accounts like TOTALLY_A_DRUMPF_SUPPORTER_0156103481 and their copy-pasted death threats and shit and gussying it up a bit. Maybe some "proof" that "Trump was just the beginning." Maybe they start rounding up some of the more outspoken right wingers online and toss them in jail, 1/6 style. No trial -- no need, they already know they're guilty.
You'd have RINOs like Romney explaining to the poor stupid GOP base that "he really respected Trump" but "really Trump reaped what he sowed" and "the rhetoric online has reached a domestic terrorist pitch that can never be allowed again" which would be why the new Bipartisan bill restricting the first amendment for online use is absolutely vital to prevent another Trump. Er, sorry, another tragic "Trump event." I mean after all, the founding fathers wrote the constitution when the furthest your speech could reach would be shouting at someone, they never intended for non-Journalists to be able to speak to everyone in the world at will. And these "assault words" are clearly not intended to be protected by the 1st amendment.
And of course, Biden/Harris or Harris/Clinton would happily sign that bill, while smirking at the camera, confident that the fix is in and no one can do shit to stop them.
I don't know where the breaking point is, but I'm pretty sure it would have been crossed somewhere before that smirking face appeared on the Camera. And then, god only knows what would happen when a nation full of people who feel they have been disenfranchised -- TWICE -- then had their economy ruined, their careers taken from them for refusing to get the 16th booster, their kids' futures destroyed... God knows what they'd do.
But I do hope they'd livestream it.