It's the definition of "begging the question." A fallacy."Everybody knows" Biden is a crook. "Everybody knows" the election was rigged. "Everybody knows" Democrats are communists. "Everybody knows" Trump is an honest genius.
So if you disagree with them, you must be lying, because "everybody knows" they're right, that they "speak the Truth". They don't have to actually prove it, because "everybody knows" it.
This is what happens when a subculture becomes detached and insulated within its own reality.