If it's BS, call them on it with something along the lines of "We dispute the veracity of this claim. Further, the alleged conduct is a felony, so if the client genuinely believes their allegations, we encourage them to file a criminal complaint at their local police station." This conveys "client is a nut, we are professionals, and we can prove it" whereas arguing the details of a case with confidential info in a public forum is wildly unprofessional and sometimes illegal.