For example (forgive my lack of details or possible inaccuracy but it's mainly to describe the concept anyway):
At one point in time in Australia, the Greens party pushed for strong climate regulation. But it was knocked down and a half-measure was proposed instead. Rather than accepting this half-measure, the Greens rejected it in favor of pursuing their original goals which they determined to be too crucial to abandon. As a result, there was no change implemented at all and it arguably impeded progress.
The Greens were accused of "letting the perfect become the enemy of the good". But as Greta Thunberg said, "'The good' in climate terms is not safe and is closer to black comedy than reality."
Whether or not they made the right decision with the gamble at the time since they didn't have the benefit of retrospect that it wouldn't work out the way they hoped, could it be that in a dire situation, there is an argument for risking causing an even worse outcome in order to attempt to pursue a better outcome which is seen as absolutely required, rather than accepting a positive yet insufficient outcome? Would that necessarily be a fallacy or possibly just somewhat recklessly ambitious in a way that might be subject to interpretation on whether it was wise or not depending on the circumstances and the importance of meeting a goal?
Also, the phrase "letting the perfect become the enemy of the good" is often associated with the Nirvana fallacy or the perfect solution fallacy.
"The Nirvana Fallacy occurs when someone dismisses a realistic solution to a problem because it is not perfect, and they argue that a perfect solution is the only acceptable option. In essence, it's the rejection of a good or adequate solution because it doesn't meet an ideal standard.
The Perfect Solution Fallacy arises when someone rejects possible solutions because they believe these solutions are not perfect or do not solve the entire problem. It involves demanding that a proposed solution must be flawless and comprehensive, or it is deemed unacceptable.
The Nirvana Fallacy is about rejecting realistic solutions because they fall short of an ideal, while the Perfect Solution Fallacy is more about demanding an ideal solution and dismissing anything less."
I struggle to understand the difference between the 2 closely related fallacies, but my understanding is perhaps the Nirvana fallacy involves: "This solution is imperfect, and the perfect solution would be unrealistic, therefore we shouldn't try to improve anything at all." (ignoring that any improvement is better than nothing) whereas the perfect solution fallacy is more like: "This solution is imperfect, therefore we should reject it and only strive for a perfect/adequate or better solution." (ignoring that the perfect solution may be unrealistic and an imperfect solution may be a valid compromise to fall back on.) The Nirvana fallacy seems overly pessimistic/defeatist whereas the perfect solution fallacy seems overly optimistic in an unreasonable way of not accepting a valid albeit imperfect solution even when there's no reason not to i.e. it wouldn't prevent the perfect solution from still being pursued.
What the Greens did in this scenario seems more like the latter, however I feel like there's a slight difference, since they didn't just reject the imperfect solution (and take an all-or-nothing approach to pursue a perfect solution) purely because it wasn't perfect, but because there was reason to believe that only one solution could be pursued and either one would make the other impossible to achieve; in other words if the lesser solution was accepted it may prevent the chance of achieving the greater solution, and vice versa, so they rejected the insufficient solution only as a means to attempt to attain the "sufficient" solution which they viewed as absolutely necessary or non-negotiable.
So does it fall under one of these fallacies, or a different fallacy, or is it not a fallacy?
Lol, yeah Eisel is a bit of a mixed bag. Quite a controversial figure in the vegan community who many disagree with on a lot of things. But I think the actions he advocates for are probably positive for the most part (not destroying nature, not exploiting animals etc, even extending that further than a lot of vegans will by saying we shouldn't own pets etc), even if his views, ideas and expressions can be problematic. I agree that part especially at the end about saying non-human animals are "mindless" didn't sit well with me, and the implication that their lives aren't very meaningful. It also continually surprises me that he actually cares about not harming/using animals given how lowly he sometimes speaks of them in comparison to humans and how focused he is on the supposed greatness/potential of humanity and civilisation. For him, veganism/animal rights is a "civilising mission" for humanity to stop doing barbaric things for the good of our own evolution, as much as or perhaps even more than it is for the good of the animals themselves. I think you're right that it's a more than slightly egoistic and anthropocentric perspective for sure. But again, at least he seems to place some value on non-human animals sufficiently to the degree that he maintains it's not acceptable to abuse them, and holds fairly high standards for that comparably to his standards for human rights. I primarily mention him in the topic of this post as one of the only people I'm aware of actively speaking out about the concept of petism / pet ownership and why vegans/animal liberationists shouldn't support it, rather than for his other musings. He rarely focuses on one point at a time and usually drags in multiple other topics into the discussion, lol, so it's hard to find him talking exclusively on that issue for reference. Like you said his book quotes are pretty eloquent.