In Love Without Conditions, Jesus tells us that you don't turn your cheek so that the other person can slap you on it, but so that the person can see that you haven't been harmed. Yes, the attack happens because the person forgot your true identity, as well as his own. If you show him the damaged cheek, you make the attack real. When you remember the truth about yourself and about him, the attack is forgiven, undone, canceled out. You don't blame him, and he doesn't have to feel guilty.
Some people think turning the other cheek is a sign of weakness.
It is anything but that. It is an act of standing up for yourself and the other person simultaneously. You are not allowing the other person to intimidate you, nor are you responding aggressively. You are standing your ground without attacking. Jesus teaches absolute truth, not relative truth.