In the Beatitudes, Jesus tells us "blessed are the peacemakers" (Matt. 5:9). Elsewhere in the Sermon on the Mount he tells us "if any one strikes you on the right cheek, turn to him the other also" (Matt. 5:39). From such verses you have apparently concluded that Christianity is a pacifist religion and that violence is never permitted.
But the same Jesus elsewhere acknowledges the legitimate use of force, telling the apostles, "let him who has no sword sell his mantle and buy one" (Luke 22:36).
You use that passage to discredit all that Jesus and Paul said about killing. Why do you think Jesus said thats enough when he was told they had two swords? Would two swords be enough to defend all the disciples? I dont believe there are any serious theologians who would ever agree with your interpretation.
So, how are these passages to be reconciled?
In broad terms, Christians must not love violence. They must promote peace whenever possible and be slow to resort to the use of arms. But they must not be afraid to do so when it is called for. Evil must not be allowed to remain unchecked.
Added weight is given to this realization when one recognizes that Scripture -- all of Scripture -- is inspired by God (2 Tim. 3:16). This means that the Old Testament is just as inspired as the New Testament and thus an expression of the will of Christ.
Jesus addressed the Old Testament teachings when he said: (Matthew 5:43-44) You have learnt how it was said, you must love your neighbor and hate your enemy, but I say this to you: love your enemies and pray for those who persecute you. And, (Matthew 5:17) Do not imagine that I have come to abolish the Law or the Prophets. I have come not to abolish but to complete them. I tell you solemnly, till heaven and earth disappear, not one dot, not one little stroke, shall disappear from the Law until its purpose is achieved.
The Old Testament acknowledges frankly that there is "a time to kill" (Eccles. 3:3). At various times in the Old Testament, God commanded the Israelites to defend their nation by force of arms. Yet it was always with the recognition that peace is the goal to be worked for. Thus the psalmist exclaims, "how good and pleasant it is when brothers dwell in unity!" (Ps. 133:1). Peace is the goal, but when it cannot be achieved without force, force must be used.
In the same way, the New Testament sets forth the goal of peace but acknowledges the legitimate use of force. It does so by John the Baptist's acknowledgment that Roman soldiers, whose job it was to enforce the Pax Romana, or "Peace of Rome," could keep their jobs (Luke 3:14) and by Paul's observation that the state "does not bear the sword in vain" but is "God's servant for your good" (Rom. 13:4).