Klein's case is about copyright (and a somewhat thin claim at that; it sure smells a lot like "I'm attempting to use copyright to quash criticism of me," and if the judge decides that's what's actually going on, he's going to lose his case). Unless I missed an update, he's suing Reddit to try and de-anonymize some people running the subreddit so that they can be properly the target of his copyright lawsuit.

Worth noting: he does not appear to have filed for defamation, which would be the thing he could complain if what they were saying was materially untrue.