As Christians we are commanded to love God and our neighbor, even including our enemy.
It is not a matter of a Bible verse here or there, it is fundamental to our faith.
You might as well ask if it is okay to worship Satan.
"Bless your persecutors; never curse them, bless them... Never try to get revenge: leave that, my dear friend to the Retribution. As scripture says: Vengeance is mine - I will pay them back, the Lord promises. And more: If you enemy is hungry, give him something to eat; if thirsty, something to drink . By this, you will be heaping red-hot coals on his head. Do not be mastered by evil, but master evil with good ." Romans 12:14,19-21
The new standard is higher than the old.
It originated with Augustine in the fifth century.
None of the early church Fathers supported anything like it.
Nothing in the New Testament supports anything like it.
"I am the soldier of Christ: it is not lawful for me to fight."
"If this conduct of mine is ascribed to cowardice, and not to faith, I will take my stand unarmed before the line of battle tomorrow, and in the name of the Lord Jesus, protected by the sign of the cross, and not by shield or helmet, I will safely penetrate the ranks of the enemy". He is ordered, therefore, to be thrust back into prison, determined on proving his words true by exposing himself unarmed to the barbarians. But, on the following day, the enemy sent ambassadors to treat about peace and surrendered both themselves and all their possessions." Severus, Life of St. Martin Chapter IV.
St. Martin eventually went on to become the Bishop of Tours and is the patron saint of soldiers.
"[Jesus said] Do not be afraid of those who kill the body but cannot kill the soul; fear him rather who can destroy both body and soul in hell." Matthew 10:28
But Jesus answered him [the devil], "Scripture says: 'You must do homage to the Lord your God, him alone must you serve.'" Luke 4:8 (Dt 6:13)
Jesus replied [to Pilate], "Mine is not a kingdom of this world; if my kingdom were of this world, my men would have fought to prevent my being surrendered to the Jews". John 18:36
This is true but not if the officials order immoral actions. Many early Christians were persecuted merely for not eating meat offered to idols or not worshiping the emperor as a god.
The Romans certainly weren't persecuting the early Christians because they were fine upstanding citizens.
I cannot believe that the God who created the universe from the largest of galaxies down to the smallest of sub-atomic particles and holds them all together in the palm of his hand needs you or I to pack a gun and go off and kill people to make things "right" in the world.
It is a profound denial of God's power.
To feel that one has this right to decide who is to live and who is to die, who's life is important and who's is not, is to me the ultimate sin of pride.
It is ridiculous to advocate that one can love ones enemy and kill them, endanger them or destroy their property.
I believe that to advocate such a position is anti-Christian.