It doesn't really matter if the ethical issues are tangential to the mission if the organisation can't disentangle itself from them. But in this case of the FSF the issues are not remotely tangential, they are deeply interfering with the mission. Almost all the leadership have been tainted by a clear refusal to put safeguards in place about leadership misconduct. It wouldn't be acceptable at a public corporation, and FSF claims to be a principle-driven organisation.

I don't see the rust situation as a massive rupture -- they did several things wrong and their process for handling it was clearly broken, and they will choose a new team who will have process and policy to the forefront of their considerations. Refusing to use rust because of some (so far, short term) management issues is an excessive response.