That's like, totally your opinion. Blizzard has a huge base in China that is largely invisible to us. As a large (gaming) company you want to stay as neutral as possible, or at least that's what I imagine what large PR firms would consult Blizzard to do.
I’m sure allowing this wouldn’t do much for their reputation as a company that wants to trade in China. Not everything has to be a forum for political speech, and trying to force everything into being one is just a deceptive way of trying to force your views onto others.