If I were Harry, I wouldn't sue to wrest back control of the charity. As others have rightly pointed out, it would only further disrupt the charity.
But if I were Harry I absolutely WOULD be consulting libel lawyers and getting a few shots across the bow in the form of a cease & desist letter or two. Because Dr C has basically accused him of bullying, racism, misogyny, and then using the media to play victim and swing the story.
These allegations are very serious on a personal level because they go against everything the Sussexes stand for, which is progressivism, truth, service and love. They have both spoken out strongly about the bullying and racism they suffered.
Warriors for Truth is a key part of Harry and Meghan's brand. They cannot let this lie. It will damage all of their future endeavours, perhaps fatally.
We know that Harry and Meghan are highly principled individuals, because they keep telling us so.
So, I am sure we will be hearing their side very soon.