@Jodi37 having the guest say "We want to resolve this without posting unfavorable reviews." is so perfectly extortionate that if you looked up "Extortion" in the AirBnB dictionary, those words would probably be in the definition.
You can get ahead of this by contacting AirBnB support *now* while this is still happening.
Have customer support review the situation and read the threatening messages from the guest (I assume you are only communicating via AirBnB messaging?). Get some support and advice from customer service now, before things really get out of hand.