You do not know how much you make me want to punch you in the loving richard. How the hell does it stop griefers? If I make a server, and someone asks me to whitelist them, and I accept them, what stops them from griefing? Seriously people, use your loving head.
The fact that you can easily filter a small population, rather than a large random one.
Sure the people you can whitelist can grief, but you can easily reverse that, because you don't have 10 random people per hour doing it.