Not in private spaces they don’t. If you play Blizzard’s games you have to abide by the rules and polices Blizzard sets. Free speech in the US means a person can talk critically about the Government or Leaders without fear of being arrested - like autocrats/kings/dictators would do if you said something the leader did not like or was negative about them.
In private spaces like a video game owned by a company, their rules apply. You can say what you want of course, and not be arrested, but they are free to remove you from their private space.
As Boubou said, Silenced accounts are currently impacted by a bug that prevents them from making a game in D3. That will lift after your Silence is over.