The government shouldn't be able to lock you up for your expression, but we are talking about if Blizzard can stop an employee from expressing a view on their product. How can you possibly enforce that anyone should be allowed to express anything in that context? How must time be allocated? Who must be allowed to speak? Can they promote rival products or badmouth Blizzard?
Free speech - for people you agree with. Well, I'm glad we sorted out that mess.