Thank their lawyers for the excellent legal advice, and then forbid them from sending the C&D because its such monumentally bad PR. Follow that up by instructin

Thank their lawyers for the excellent legal advice, and then forbid them from sending the C&D because its such monumentally bad PR. Follow that up by instructing them to find an alternative way to deal with possible trademark issues. The best course of action from a legal perspective is often not the best course of action from a business perspective.