I think you _never_ take secretive action. You don't go behind someone's back.
They should have said, "Sam, we think you are wrong, we think we are right, and we think you are not listening, so we are going to take this to the board."
They should not have conspired.
Don't conspire.
Also, in my experience, in a situation like this where sides A and B see things differently, and side B can't convince side A they are wrong, _both_ sides are usually wrong. People can easily see how others are wrong, but often find it harder to see how their position is also wrong. The solution is to keep talking it out. Until that correct position C is found.
When Side B is so confident that they are right and take secret action against Side A, not only do they still get things wrong (because the still yet to be discovered idea C is the correct position), but they are guilty of dishonest behavior, as those that conspired against SamA are here.
IDK what the dynamics inside OpenAI are like. In nearly all scenarios, I would agree with you, but if sama is really a master manipulator like some people are saying, then some level of secrecy/conspiracy might have been necessary to escalate to the board without being pushed out of the company first.
Let's take an extreme hypothetical where Sam instructs you, an OpenAI exec, to take Action A, and says, "I'm a very influential person. If you don't do what I say or if you make me look bad, I'll use my connections to make sure you never work in the Valley again." Responding with "I disagree, and I'm going to go to the board about this" might be incompatible with future employment, especially if the board doesn't take your side. Going to the press might also be a disaster given sama's history of emerging unscathed from Worldcoin, his sister's allegations, etc. The best choice for most people is probably to just stay quiet and do as you're told. Later, when the board comes to you investigating claims of abusive behavior, you might share with them but request anonymity, because you know that Sam is indeed a very influential person; if the board decides not to fire him (or if they do and it doesn't work), you will be ruined.
In this situation, all the board can do without breaking anonymity is to say, "we have investigated and discovered incidences of abusive behavior, and for that we are removing you as CEO."
I like what you did here. You steelmanned their argument.
That being said, I think in that case, if it is something you believe so fervently in that you are willing to conspire, then the correct course of action is to not conspire, but resign or stand up to him, and, as you say risk being "ruined".
I never see a reason to conspire.
Better to have everything taken from you but keep your integrity, rather than the other way around.
(Disclosures: I know SamA personally from interactions years ago and have high opinions of his character, even though I disagree with him strongly on open source and secrecy [I'm on the extreme end of that one]. I also have the distinction of maybe being the only person person accepted into YCombinator twice and kicked out for standing up for something I believe in).