To put it simply, blaming Democrats (or the left) for the right's behavior -- or for Trump possibly getting re-elected -- is relying on a false paradigm. Elections don't hinge on rational responses to policy minutiae in a vacuum. Everything passes through media of some sort, and the right's sources of information are dominated by a top-down movement that seeks to enrich itself and entrench corporate power at any cost. After all that has been revealed about Fox over the last year, we know this to be true, yet some people like to pretend it never happened! As far as the left's behavior is concerned, the worst and very non-representative examples of overzealousness from someone on social media or elsewhere will always be cherry-picked and blown out of proportion.
As a commenter mentioned below, there is a name for this assumption that Democrats are responsible for everything Republicans do: "Murc’s Law." According to David Roberts, who is quoted in the post:
This is not some quirk, it is central to reactionary psychology. Every fascist (and fascist-adjacent) movement ever has told itself the same story: our opponents are destroying everything, they’re forcing us to this, we have no choice but violence.
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