Not really. In this analogy I know this group exists and plan for, with, or around them. If vegans found an activist group that better aligned with their goals why would I be surprised or upset they went to that one?
If that activist group then campaigns against the "imperfect" initiative, sinking it by 1% point, why wouldn't you be upset at them? "It's just politics, it's just their point of view" isn't a particularly left outlook, it's... well, very 'moderate suburban liberal'. Politics are often a matter of life and death - in the most literal sense. Being upset is pretty low on the totem poll for intensity-of-reaction with that in mind.
None of this is surprising, or at least it shouldn’t be. We know how people actually behave.
Not being surprised that some people are self-defeating and being upset that people are self-defeating and that other, ostensible allies are defending them for being self-defeating and encouraging them to continue being so are two different things.
I'm not surprised, for example, that bootlickers vote for Trump, or that there are millions of bootlickers in this fucking country. But I am upset about it. I'm not surprised that there are a significant minority of leftists who prefer purity politics to averting and reducing genocide. But I am upset - and I don't think that normalizing it in the communities I frequent is something that I should stand by and be quiet about.
Further more in this analogy the animal rights group isn’t campaigning to stop puppy farms, they’re campaigning for puppy farms. Of course people that care about animal rights didn’t support them.
Campaigning for regulation of puppy farms, let's say, since the Dems were quite clearly not anti-Israel, but had clearly shifted to a less pro-Israel position, especially after Biden dropped out.
In that view - when faced between making puppy farms less horrific or letting them continue as usual - or even making them worse - why should I not be upset that an ostensibly anti animal suffering group opted to let suffering continue or intensify instead of stopping it out of some bizarre sense of purity.