But you are making a separate contention now: that employees are spent considerable company time on discussions of politics. If they were, up till now it was with the endorsement of their managers.
The Basecamp policy is now that you can't discuss politics (or anything controversial) on any company platform, including e.g. in the break room, on the discord chat or whatever on your commute, out of office hours, etc. And they are officially removing any feedback mechanisms from company structures, figuratively salting the earth to prevent anyone discussing anything.
Obviously everyone could move to a platform in the cloud for discussions, but the writing is on the wall.
While this may well be a gross violation of labour laws, US employee rights are so weak it doesn't matter: say anything and you're canned.