This is just the fallacy. Political groups are coalitions not single monoliths.

In general, hypocrisy is a pretty weak argument. It's an annoying personality trait, but consistency is a thing humans often fail at, and humans failing at holding consistent opinions is a failure of those humans, not the claims they're making. It's not quite as weak as the more non-sequitur kind of ad-hominem attack, because it does at least pertain to the argument being made, and kind of resembles a logical contradiction if you squint, but it seldom does a good job addressing the merits of the argument, rather than the arguer. It's a successful political tactic for the same reason ad hominem arguments in general are, of course, especially in the context of representative forms of government, where the person's character or competence is relevant when they're running for an office. Much less so in contexts where the merits of a position are being debated in abstract.

I think it's very silly to make the argument that "groupwise hypocrisy" is not a fallacy in such a conversation. In politics, the reality is that people have to form coalitions with people with whom they don't agree on everything, and non-political groupings are even more non-sensical, often holding people responsible for the opinions of other people who happen to share things like inborn characteristics. It's especially ridiculous to explain this with this idea that people are engaging in some kind of elaborate coordination to argue with you on the internet. Yes, some people, and indeed political parties, engage in that kind of behavior, and if you think you're arguing with something like a botnet, there are larger considerations to make about what you gain as an individual by trying to engage with such a machine at all. If I believe I'm arguing about the merits of an idea with an actual person, and I find myself reaching for something like "your group is collectively hypocritical on this issue" to make my argument, this is cause to reflect on whether I actually have any real arguments for my position, as that one is... well, essentially meaningless

I think you're trying to invoke what's commonly called a "motte-and-bailey" argument, where people argue for a maximally-defensible position when faced with serious criticism, but act as though they're proving a much less defensible version of their argument, often including a nebula of related ideas, in other contexts. This is something individuals and coordinated factions absolutely do, but again doesn't really support treating any grouping you want to draw of some kind of collective hypocrisy. Even assuming we care about hypocrisy, it seems like this kind of reasoning about nebulous groups that don't explicitly coordinate would allow making that argument about any position in any context, depending on how you draw the boundaries of the group that day. It's well-understood that you can go on the internet and find someone who believes just about any crazy thing you can think of, or find someone who makes the argument for any position poorly.

Is it true that they don't appear in the threads where you feel it's obvious they're in the wrong? Or do they just get upvoted less in those threads so you don't see it when they do appear?

It's almost as if factions are made up of different people with different opinions in a loose alliance.

But nah, clearly they're all goombas.

This is exactly it. You see it on HN all the time. You will debate someone. Then deep in thread, a second person appears with a gotcha. when you point out that the gotcha doesn't fit in with the prior argument, they point out that was a separate person. They knew damn well what they're doing with their little conniving deflection fuck-fuck game. They're acting for the same surrogate argument. The Goomba is real and the people playing the game are just too cowardly to be two-faced themselves so they act two-faced through a surrogate and deflect to the surrogate when it's pointed out.