> Post-election analysis would show that the Bernie Bro trope was entirely constructed; there was no evidence to show that young white men made up a majority of Sanders’s supporters.
The author just takes it as a non-controversial statement of fact that "white men" are inherently evil and that if they support a political candidate that means the candidate is also bad, and that she needs to distance herself from the whole thing.
The story arc isn't that anything changed about Bernie's policy views, history or anything else. The bad thing that happened is a rumor that "young white men" liked him, which was bad, and the good news was that Bernie supporters were actually from the morally good races and genders.