Received A Cease And Desist Letter From An Ex Friend, Do I Need To Respond? (fl)

I went no contact with a friend back in October, I had a convo with them about why I was ending our friendship but they didn’t seem to get it.

I received a cease and desist letter from his attorney yesterday, saying that I defamed his character and that he’s entitled to damages bc of mental health impact.

The letter was specific about my alleged defamatory statements him and requests that I “retract my statements by X date”. No other response requested.

How do I go about retracting statements I never made? I’m planning on ignoring this because idk how anyone can prove that I retracted anything

(this is more a curiosity question, I’m currently in the process of applying to law school)