Evil deeds are committed by people every day, but I don't believe Human Beings are capable of being wholly or genuinely evil, regardless of how their obituary is written.
And to tie it into Star Wars...the whole lesson of the saga is to suggest that good can be found in even the most seemingly evil person. That suggestion that someone as evil as Darth Vader could be redeemed and that underneath it all he was a father who cared about and loved his children speaks to the Humanity...that kernel of absolute, indestructible Good...inherent in all of us. And if there wasn't some measure of collective truth to that lesson, then we would've walked out of the theater in 1983 laughing at the mere audacity of it.
--ID