"there was an exchange that resulted in him being banned"
Well it's simple then : publish the content of the exchange and show everyone what happened. Because there's a good chance that somebody started to be insulting and the other someone didn't appreciate and shot back. So publishing the exchange will settle the matter.
Then Twitter can get outraged again and we'll know if we need to bang on Valve to reverse the decision or not.
But of course, that won't happen, because it would be a breach of confidentiality or something. Too bad.