The more relevant part is probably "OpenAI’s mission is to ensure that AGI ... benefits all of humanity".
The statement "it would be consistent with the company mission to destroy the company" is correct. The word "would be" rather than "is" implies some condition, it doesn't have to apply to the current circumstances.
A hypothesis is that Sam was attempting to gain full control of the board by getting the majority, and therefore the current board would be unable to hold him accountable to follow the mission in the future. Therefore, the board may have considered it necessary to stop him in order to fulfill the mission. There's no hard evidence of that revealed yet though.
The statement "it would be consistent with the company mission to destroy the company" is correct. The word "would be" rather than "is" implies some condition, it doesn't have to apply to the current circumstances.
A hypothesis is that Sam was attempting to gain full control of the board by getting the majority, and therefore the current board would be unable to hold him accountable to follow the mission in the future. Therefore, the board may have considered it necessary to stop him in order to fulfill the mission. There's no hard evidence of that revealed yet though.