I understand this concept is not accepted among the majority today, at the least, it's probably "pushed back on" by many Brothers and Sisters of faith. However, I can't help but read time and again in the New Testament Scriptures where the idea of retaliation or self defense is spoken against. So many before us, Peter, Paul, Stephen, Jesus, etc. lived out those Scriptures themselves choosing to neither retaliate or defend themselves by physically harming someone else. How is either mentality justifiable, then, when compared to the Word?
The apostle Paul outlines for the Romans in chapter 12:9-21 the marks of a true Christian. I will be the first to admit, I simply don't exude these qualities on most days, but I should be striving to reflect these marks not just in my actions, but also in my thoughts and attitudes toward others... even non-believers.
"Let love be genuine. Abhor what is evil; hold fast to what is good. Love one another with brotherly affection. Outdo one another in showing honor. Do not be slothful in zeal, be fervent in spirit, serve the Lord. Rejoice in hope, be patient in tribulation, be constant in prayer. Contribute to the needs of the saints and seek to show hospitality. Bless those who persecute you; bless and do not curse them. Rejoice with those who rejoice, weep with those who weep. Live in harmony with one another. Do not be haughty, but associate with the lowly. Never be wise in your own sight. Repay no one evil for evil, but give thought to do what is honorable in the sight of all. If possible, so far as it depends on you, live peaceably with all. Beloved, never avenge yourselves, but leave it to the wrath of God, for it is written, "Vengeance is mine, I will repay, says the Lord."To the contrary, "if your enemy is hungry, feed him; if he is thirsty, give him something to drink; for by doing so you will heap burning coals on his head." Do not be overcome by evil, but overcome evil with good."
Now that particular passage speaks more to retaliation, but "What about self-defense?" you ask. Well Matthew 26:47-56 gives the account of Jesus' arrest when Judas had betrayed him. The chief priests and elders came to seize him with swords and clubs. When they put their hands on him and seized him, Peter drew his sword and cut off the ear of the high priest's servant. He was trying to defend Jesus from the hurt these men wanted to cause him. But what did Jesus say to Peter in response?
"Put your sword back into its place. For all who take the sword will perish by the sword."
Jesus then reached out and touched the servant's ear and healed it. Why? Why wasn't He proud of Peter for defending Him? Why did He change the things many of His disciples had been taught through the Old Testament law... 'an eye for an eye and a tooth for a tooth' or 'love your neighbor and hate your enemy'? Perhaps Jesus was thankful that Peter was willing to stand with Him (I don't honestly know), but the truth is, He had already taught His followers to not seek retaliation and to love their enemies. Jesus himself said this:
"But I say to you, Do not resist the one who is evil. But if anyone slaps you on the right cheek, turn to him the other also. And if anyone would sue you and take your tunic, let him have your cloak as well. And if anyone forces you to go one mile, go with him two miles. Give to the one who begs from you, and do not refuse the one who would borrow from you... But I say to you, Love your enemies and pray for those who persecute you, so that you may be sons of your Father who is in heaven... For if you love those who love you, what reward do you have?" - Matthew 5:38-48 (not all verses written here)
The point is this: If we seek to harm those who harm us, how does that resemble God? He chose to show us love, mercy, grace, and compassion when we were His enemy! He sent His Son, Jesus Christ, to be rejected and abused beyond recognition, to die a horrible death in order to make a way for us, His enemy, to be justified in our sins and reconciled through faith, to be in His presence for all eternity. He could have retaliated and given us what we deserved, He could have defended His name and wiped us all off the face of the earth... again... but He didn't! When we fully grasp how much pardon He extended to us while we were His enemy, we should desire to do the same to our enemies because that would make us the most like our Father.
Can I live out what I'm teaching my children? Can I bear in my body the marks of a true Christian? If I am unwilling to do so, I am merely teaching my children hypocrisy. I must crucify my fleshly desire to defend or retaliate... I must choose to walk in the Spirit as Jesus did, showing mercy and grace to my enemies as my Father did.