Well, obviously I'm not going to let anyone hit me, but I've always interepreted the verse to mean - don't be like them!
People might be nasty and rude, or narcissistic and self-centered, but don't be like them. Don't respond to their rudeness or narcissism with the same thing. Don't let people drag you down into their bad behavior.
Be a better person, take the high road.
Very simplistic it seems, but it works for me.