The best argument in my opinion against "nothing to hide" is that you don't get to decide that. The accuser does. If that doesn't scare you then you didn't think it through fully.

A change in regieme is a downright terrifying variant of Pascal's Wager - where you are judged for heresies against ideologies that were obscure or didn't even exist yet.

The Khmer Rogue made being an intellectual or wearing glasses something to hide. All sorts of absurd ideological hypotheticals become terrifying.