The New Testament verse that overides violence is the very one you have been denying or twisting to your advantage from the beginning. Jesus referenced an eye for an eye passage from the Old Testament and He said, BUT I SAY UNTO YOU, meaning He is making a change. He is saying to turn the other cheek now. To not render evil for evil. To do good unto your enemies and to bless them that curse you and to pray for them. For vengeance is mine, saith the Lord. Yet you want to take part in that vengeance and strike back when they hit you accross the cheek. But in doing so, you are violating the Lord's command to turn the other cheek (Which is in reference to physical justice in the OT). He says don't hate your enemies but love them. Hitting them back and or shooting them is not loving your enemies.
Many times when Christ spoke, his disciples and other people misunderstood him to be speaking about physical things when Christ was talking about spiritual things. For Jesus said he had meat that they did not know about in John chapter 4. Jesus was speaking in spiritual terms for the meat He spoke of was doing the will of the Father. Nicodemus initially thought Jesus was talking about physical birth when Jesus told him he needed to be born again.
I believe Jesus allowed Peter and the others to buy a sword (i.e. the wrong kind of sword), so that Jesus could prove that He did not want us believers using physical swords because Jesus rebuked Peter for using his sword and said He could have called down a ton of angels to protect Himself. Also, Jesus made a very important statement that is not in your favor, too. He that lives by the sword shall die by the sword. Meaning, if you take up the sword as a way of life, you are going to die by it. This was not a postive statement by our Lord Jesus Christ but it was a negative statement as a part of Jesus rebuking Peter.
This is to the state (Who are unbelievers) and this is not for the believer who is supposed to remain unspotted from the world.
Would I be advocating violence by calling the police because they carry guns? No. I am not. First, if it is a situation such as a riot and or a violent situation that has gotten out of control, the police are God's ministers of justice. This is what Romans 13 talks about. If I find that my prayer for the stopping of the violence immediately and my rebuking of my enemies is not applicable to the situation, then God can and does use unbelieving law enforcement officers to bring order to the situation. I realize that there is a time where God can intervene to protect me and my loved ones, and there are times when I realize that I may have to be persecuted for my faith, and there are times, that God wants me to submit to the authorities in power by doing everything I can to bring peace and order to a bad situation. I can pray that the police resolve the situation with as little to no violence as possible. But it is not in my hands. What the police do or not do with their guns is up to them. They may decide to resolve the situation peacefully or with little to no violence. It's not like I am calling a hit man to take everyone out. The police are to protect and to serve. They are to bring order. But is that the call of a believer? To be a police officer? While I do not believe it is a sin that leads unto death to be a police officer who takes lives in self defense. I believe there are saved Christian police officers. However, I believe if an officer truly wants to follow Jesus to the most truthful extent, they will in time be leaded to forsake everything for the cause of Jesus Christ (Realizing that the ways of this world are far different than the ways of the kingdom of God).