Continued:
Verse 20 - "Them that sin reprove before all: that the rest also may have fear."
Sean got this one already, but I'll just add that this says "Them that sin". The whole point of what Sean quoted was how to establish if someone has sinned or not, if the person is a priest. So obviously there is no need to reprove a priest before all, that the rest may have fear, if it is not certain that a priest has sinned to begin with, which needs at least two witnesses to be established.