"[A]nd we who were filled with war, and mutual slaughter, and every wickedness, have each through the whole earth changed our warlike weapons — our swords into ploughshares, and our spears into implements of tillage— and we cultivate piety, righteousness, philanthropy, faith, and hope, which we have from the Father Himself through Him who was crucified; [...] Now it is evident that no one can terrify or subdue us who have believed in Jesus over all the world. For it is plain that, though beheaded, and crucified, and thrown to wild beasts, and chains, and fire, and all other kinds of torture, we do not give up our confession; but the more such things happen, the more do others and in larger numbers become faithful, and worshippers of God through the name of Jesus. For just as if one should cut away the fruit-bearing parts of a vine, it grows up again, and yields other branches flourishing and fruitful; even so the same thing happens with us. For the vine planted by God and Christ the Saviour is His people." -St. Justin Martyr, Dialogue with Trypho, 110
"We offer you the wholesome help of our mind and advice. And because we may not hate, and we please God more by rendering no return for wrong, we exhort you while you have the power, while there yet remains to you something of life, to make satisfaction to God, and to emerge from the abyss of dark superstition into the bright light of true religion. We do not envy your comforts, nor do we conceal the divine benefits. We repay kindness for your hatred; and for the torments and penalties which are inflicted on us, we point out to you the ways of salvation. Believe and live, and rejoice with us for eternity, you who persecute us in tithe." - St. Cyprian of Carthage, Treatise 5, An Address to Demetrianus Proconsul of Carthage, 25
I'm not going to stand here and say self-defense is wrong. But if you are going to ask what purpose would it serve to give up your life for someone who attacks you, who hates you, then the answer to that is found in Christ's words to us in His Sermon, in the example He established by His life, suffering, and death; in the words and promises of Scripture, and in the testimony of the ancient and holy Fathers of the Church. Two of which I have provided here for consideration.
To wit: Even should our bodies be cut down, our blood and our suffering--in patience, kindness, and unrestrained love--with the faithful confession of Christ in our lips, becomes the seed scattered upon the ground which God shall make grow. So that even in the ones who despise us, who have put us to death, shall grow in their heart a faith which shall become their salvation.
We have lived so distantly and far apart from the time when being a Christian actually cost us something. We who have lived our lives where being a Christian has been to our advantage, not our disadvantage, can scarce contemplate the depth of faith which our spiritual predecessors experienced. They were rock stars, and we are--for the most part--mere poseurs pretending at taking up a cross.