All of the tweets linked seem pretty direct and transparent (i.e. the opposite of passive aggressive). Unless you're seeing some tweets that aren't in this thread?
That said, I think there are quite enough "openly woke" companies that it's not going to be hard for any of these people to find a welcoming home. Especially if they manage to successfully play the martyr on social media. This is where our society is at right now.
Overall this is probably a win/win -- the employees who left were surely the ones most dedicated to keeping the office political. Basecamp got rid of them and can rebuild with a team that's more aligned with the new policy, and those employees can find new jobs at companies that don't mind being political.