I would try suing for damages, especially if their claims are denying you the ability to make money. I think you might be able to sue for slander as well, since they made the claim that you are stealing licensed material, which will affect your reputation as a producer of original content.
I don't see how one could consider this slander/libel, since the allegation was completely private until publicized by M dot Strange. Obviously reputation would not have suffered if the claim remained private.
