You can't be proven 100% innocent, you're just assumed to be innocent in the court of law until you're proven guilty. Outside the court, you are whatever the the forget the public believes you are unless shown elsewise. That's why suing for libel / slander is a thing, to get on top of anything that would affect public opinion before it damages your reputation or brand.
Let's say Kavanaugh was completely innocent, there's no reason for him not to want there to be a curated investigation into the matters. This way, there can't be any theoretical "Witch hunt", and his reputation doesn't get slain.