The Democrats are in full McCarthy show trial mode. If it were an honest inquiry then maybe is would make sense to talk to them. Henry Waxman’s treatment of Victoria Toensing made that obvious to everyone.
They’re not looking for “the truth” or anything close to it. They’re looking for anything that they can spin into a “scandal”.
Better to take the Fifth than to join Scooter Libby in being sacrificed for the Congressional soundbite.