You suspect someone in your community is a bad actor. Kinds of reasons not to move against them:
This is all from-first-principles. I'm interested in takes and reading recommendations. Also creative affordances / social technology.
The convenient case would be that you can privately get the powerful stakeholders on board and then they all oust the bad actor and it's a fait accompli, so there's no protracted conflict and minimal cost to you and your community. If you can't get the powerful stakeholders on board, I guess you give up and just privately share information with people you trust — unless you're sufficiently powerful/independent/ostracized that it's cheap for you to make enemies, or it's sufficiently important, or you can share information anonymously. If you're scared about telling the powerful stakeholders, I guess it's the same situation.
This is assuming that the main audience for your beliefs is some powerful stakeholders. Sometimes it's more like many community members.
More reasons:
2.b. The problem is not lack of legible evidence per se, but the fact that the other members of the group are too stupid to understand anything; from their perspective even quite obvious evidence is illegible.
7. If you attack them and fail, it will strengthen their position; and either the chance of failure or the bonus they would get is high enough to make the expected value of your attack negative.
For example, they may have prepared a narrative like "there is a conspiracy against our group that will soon try to divide us by bringing up unfounded accusations against people like me", so if your fail to convince the others, you will provide evidence for the narrative.