Here's another argument against the Green obsession with defeating the Democratic presidential ticket:

That tactic alienates the largest potential group of people the Greens or other independent Left parties might win over- progressives who have spent much if not most of their lives working within the Democratic Party, and who are increasingly alienated by it's rigid militarism and Eisenhower Republican(except where they are to the right of the Eisenhower Republicans) policies, but who are terrified of a long period of far-right rule in which far right administrations would never be under any constraints- we can assume, from here on in, for example, that there will never be any more "decent Republicans" stepping in to rein in the Nixons/Reagans/Bushes/Trumps from making dangerous or authoritarian decisions. We can assume that, from henceforth, everyone still in any major position of of power or influence within the Republican Party will simply be a mindless automaton unquestioningly carrying out the wishes of whoever the latest Maximum leader is- or people in historically oppressed communities who have been treated like dirt by the Democratic establishment- an establishment focused solely on appeasing it's "socially liberal, fiscally Scroogelike" corporate donors and the largely imaginary block of "suburban independents" who, this establishment imagines, will only vote Democratic if that party agrees to leave more or less leave Black and Brown people out in the cold and explicitly leave workers and the poor and progressive activists totally out in the cold, and make up for this by being pro-choice, as if that is the only issue that matters- who are certain they can't count on surviving years or possibly decades of unaccountable right-wing power.

What the Greens are doing with this approach is costing them the potential support of millions, possibly tens of millions of voters in future elections, and gaining them nothing in return.