So if I get this right, a professional gamer introduced political content in his stream/interview and was then banned for one year and his prize money was revoked.
On the one side, generally, I think you should keep politics out of sports, videogames etc.. You hear about politics almost everywhere nowadays, so it would be great if there are areas that don't include it. But personally I find what Blizzard did rather harsh. I read their reasoning (violate the rule that the player did something to damage Blizzard's image), and find it a bit far-fetched, although I could see it hold up in court. Still, I assume the guy (at least partly) lives from esports, so banning him for a full year does seem harsh to me.
The Congress thing should be seen more generally, I think. The Blizzard case, as they write, is only one of a few recent cases where a foreign nation (China) influenced decisions in the US in a targeted way. I highly doubt Congress is particularly interested in that particular esport, but rather saw it as an opportunity to take a stance against that foreign influence.
I do think it's a bit 'unorthodox' for Congress to get mixed up in such a particular case, but can understand the general idea behind it.
At the end of the day, Blizzard is just a company like many others trying to maximize their income. Protesting against them might let them reconsider, but seeing how huge the Chinese market is, it might from a business side be more advantageous to stick to their banning the player.