Let me appeal to observation. When you can have the simplest facts dismissed because the source is 'left', because they weren't personally witnessed corroboration ergo automatically wrong, and the widespread prevalence of taking words for it because the individual has no interest in the five minutes of research to confirm, what more reason do you need? The majority clientele will never check nor even be interested enough to consider the dispute. Thus regular can be peddled and maintained as core to someone's beliefs simply because they heard it way back when, remember it now and it's effectively gospel that is ten times harder to uproot because it is now what they know.
Even the most rational are prone to the factors above, leading to horrifically skewed views that are never willing to self assess for lack of interest yet have impact in collective. If it serves your purposes, it is the most reasonable thing to do to perpetuate it without consequence.