If you know EVERYTHING about anybody, something out of their past will allow you to change their opinion on ANYTHING.
Worse, we have the "best" spy networks in the world which has demonstrated repeatedly that "mere mortals" have strangely and completely changed their positions overnight.
See John Roberts, SCOTUS, for reference.
I was just alluding to PJ O’Rourke’s book of that title. Other than that misunderstanding, we seem to agree on this.