.. This is a comical generalization of an entire industry which spans beyond US..
I have worked in plenty on companies (big and small) where politics was simply left outside of business and everyone was fine with simply discussing the actual system design, infrastructure and data models.
Employees were simply not permitted to attempt to convert others to Christianity or initiate flame wars regarding abortion laws.
There is a time and a place for politics and a business setting is just not it.
I think this is a great move by Basecamp and I hope more companies follow. At a minimum, their stance is now crystal clear and there will be high cohesion between employees and management.