You'd be hard pressed to find a company where leveling personal attacks against your co-workers isn't a fireable offense.
Freedom of speech isn't the same thing as freedom from the consequences of his actions. All it means is you can't be jailed or executed for it. You are not entitled to have people continue to have you in their lives.
Furthermore, his employer has a right to freedom of association, and they have chosen to exercise that right by ceasing to associate with him.
If this is authoritarian, than I will proudly call myself an authoritarian. Perhaps Hobbes was right after all.