I don't know about you, but I don't want every entertainment platform to be consumed by political discussion. Sometimes you just want an escape and that's something video games help provide.
Those discussions are worth having but there are already plenty of platforms available to have them on.
The part I find especially frustrating is the double speak. Why do they say "We encourage players and community members to express themselves" while punishing someone for expressing himself? Just be honest. "We discouraged players expressing opinions that make it harder for us to sell in other markets." That has the benefit of being honest, plus everyone knows it's the truth anyway.
It all comes down to the platform. A mod who takes down political threads on a support forum is not "discouraging community members from expressing themselves". They're moderating a forum with a specific content focus.
I definitely think it would be wrong for Blizzard to threaten any kind of punitive action against a player who is making those kinds of statements outside of Blizzard's platform.
Those discussions are worth having but there are already plenty of platforms available to have them on.