I don't know, what if someone gets a license from the government, hair stylist, restaurant, business, accounting, lawyer... and the State board has questions for you, your just saying one could ignore what they are asking you? I don't think so. Not answering might be seen as something like contempt of court.
IF, I were Moore and your scenario was pulled on me, Come in and play an hour or so game of "When did you stop beating your wife?" . . . 40 years ago, I'd tell them that even as a Congressional Committee Constitutionally granted the power of such an Investigation, they have NO Standing to either subpoena me or investigate me for anything that supposedly happened 40 years Before I Was Elected as a Senator. THEN, I'd walk out on them.
Invite them to hold their damn fool testimonies from my accusers. Sum it up any way they like, and if they uncover any real proof of criminal conduct by me, turn it over to the proper Authority in Alabama, the State AG's or Local DA's Office.
Short of that, Have yourselves a nice day, Ladies and Gentlemen of this Committee.