It's not a false equivalence because I never claimed it was equivalent. The purpose of the hypothetical is to explain a concept, not to draw a direct comparison.

Not voting for Biden is punishing Biden because it's denying him something that he wants. I'm not allowing other people to make the decision for me, it's not as if my vote passes to the next person in line or something.

Primaries are not legitimate elections. There is no oversight and no legal requirement that they be conducted fairly, or even that they be conducted at all. The democratic establishment has the ability to influence the outcome or cancel them altogether, which it exercises regularly. What should I do if the democrats said, "We're not doing primaries at all any more, we're going back to the old days where party elites select candidates in smoke-filled rooms?" Should I just give them my full compliance?

I reject lesser evilism for reasons I already explained.

I am not responsible if withholding my vote leads to an increase in people being killed. That's not how responsibility works. The responsibility is on the people doing the killing, the people ordering them to, and the people supplying them with the means to do so. It's like if a serial killer tried to plead "not guilty" on the basis that one of his hostages refused to cooperate and that caused him to fly into a rage and kill more people so it's really the hostage who should be tried for murder. It's an absurdity, and frankly it betrays a refusal, in your psyche, to hold politicians accountable for their failures and misdeeds, instead trying to shift the blame onto ordinary people.