In general, committing to any stance as a personal constant (making it a “part of your identity”) is antithetical to truthseeking. It certainly imposes a constraint on truthseeking that makes the problem harder.
But, if you share that stance with someone else, you won’t tend to see it. You’ll just see the correctness of your own stance. Being able to correctly reason around this is a hard-mode problem.
While you can speak about specific spectra of stances (vegan-carnist, and others), in reality, there are multiple spectra in play at any given time (the one I see the most is liberal-radical but there are also others). This leads to truthseeking constraints or in a word biases in cross-cutting ways. This seems to play out in the interplay of all the different people committing all the different sins called out in the OP. I think this is not unique to veganism at all and in fact plays out in virtually all similar spaces and contests. You always have to average out the ideological bias from a community.
There is no such thing as an epistemic environment that has not declared war on you. There can be no peace. This is hard mode and I consider the OP here to be another restatement of the generally accepted principle that this kind of discussion is hard mode / mindkilling.
This is why I’m highly skeptical of claims like the comment-grandparent. Everyone is lying, and it doesn’t matter much whether the lying is intentional or implicit. There is no such thing as a political ideology that is fully truth-seeking. That is a contradiction in terms. There is also no such thing as a fully neutral political ideology or political/ethical stance; everyone has a point of view. I’m not sure whether the vegans are in fact worse than the carnists on this. One side certainly has a significant amount of status-quo bias behind it. The same can be said about many other things.
Just to be explicitly, my point of view as it relates to these issues is vegan/radical, I became vegan roughly at the same time I became aware of rationalism but for other reasons, and when I went vegan the requirement for b12 supplementation was commonly discussed (outside the rationalist community, which was not very widely vegan at the time) mostly because “you get it from supplements that get it from dirt” was the stock counterargument to “but no b12 when vegan.”
California is not capable of extracting tax revenue from companies like Google in any meaningful way, so we shouldn’t expect them to be capable of taking stronger, less directly self-benefiting action. If they can’t get Google to pay them, they can’t get Google to stop AI.
What is California’s great track record in this space? They have caused “May cause cancer in California” to be printed many times. We shouldn’t expect them to save us.