Earlier this month, Blitzchung won the Hearthstone Grandmasters Tournament, and after his victory, the casters gave him an opportunity to offer a closing statement and he said "Liberate Hong Kong, revolution of our time/age." (slight variation depending on the translation)
After that, Blizzard:
a) Revoked Blitzchung's Grandmaster status
b) Stripped him of his $10,000 prize money
c) Banned him from all pro-play for a year
d) Permanently blacklisted the casters from ever participating at a Blizzard event again.
In response to this, the internet went fudging nuts and everyone from reddit to US Congresspeople across the political spectrum were condemning Blizzard for their actions, and the internet being what it is, started memeing. Blizzard was prioritizing the Chinese market over human rights and so people turned Mei from Overwatch into a Pro-Hong Kong symbol in an attempt to get Blizzard banned in China (sadly, didn't work) and after a few days, they issued a statement saying, paraphrased, "we jumped the gun and overreacted, our bad." and gave Blitzchung his money and title back and reduced the sentence on both him and the casters to six months.
After that, a lot of the buzz settled down but since then, they've banned (last I checked) an additional 3 people for supporting Hong Kong so they very obviously haven't changed their views. I've personally uninstalled all Blizzard games, Battle.net, and cancelled all existing subscriptions, but I understand some people don't feel as strongly about it.
That said, Tencent only owns 5% of Activision-Blizzard, so what they did was done out of pure greed in an attempt to satisfy China. While I won't defend it, Riot is 100% owned by Tencent so it's at least a little bit more understandable why they chat-restricted anything relating to Hong Kong during Worlds this year. About Blitzchung's banBlizzard's StatementExample of Mei memesThe reason for the statement
which was recently killed after 7 months of protests in Hong Kong.