Fatty actually lives in Arkansas, which is a one party consent state, and to his dubious credit he does make that argument in his response to the court's order. It won't do him any good though, since the court never said the recording was illegal, just highly improper.
I also highly doubt there is any breach of attorney-client privilege here, though I'm willing to be corrected by Useful_Mistake or An0minous on this. Pretending for a moment that Acerthorn could pass as competent council for David Anthony Stebbins, this is a conversation between the legal representation for both parties. Any privileged information either of them brings up to the other is already a breach of attorney-client privilege and you can't really put that genie back in the bottle once it's out. If lawyer A tells opposing council B, "look, my guy will go on the stand but you'll never get out of him that the bodies are buried under the woodshed" council B is absolutely allowed to use the information they got however they want and it's on attorney A's head for letting it get out there.
Again, not an illegal move, but one that would get any practicing attorney in a lot of trouble and likely added fuel to Google's argument for vex-lit status.