>The problem is that we've gone beyond voicing criticism to constructing parallel, unconnected realities. It's not like there's one side praising the Vietnam War and another side criticizing it, it's like there's one side saying "hey, there's a war going on in Vietnam" and another side saying "no there isn't."

We always had that too. Not for "a war going on" or not, but e.g. about atrocities "our side" did during the war (which establishment media would downplay), or private interests served by such and such law (which establishment media would hide).

Those were alternate realities (e.g. are X foreign group "freedom fighters" or "CIA sponsored death squads"), not just simple disagreements on technical points.