Please show me where the New Testament supports violence. (Unless you can do so, you're blowing smoke.)
The Pope himself has ordered people to be burned at the stake and he has ordered people to go into the crusades; go look at their reasoning.
Or you can simply look at the story of Paul: here we have a man who persecuted and killed prior to his conversion to Christianity, but all of that was forgiven simply because he accepted Jesus. But the church he founded then simply continued to commit the same acts of persecution and killing against non-Christians.
This is common to any group of people, whether or not those people are Christian.
Any sufficiently large group of people contains people who commit violence, but that's not the issue. Atheism, chess clubs, or debating societies don't claim to instill a sense of morality into their members, so they can't fail at doing so.
But Christianity is explicitly about morality, about right and wrong. Therefore, how Christians behave tells us whether Christianity is effective as a moral philosophy.
Furthermore, when we examine Christian dogma in more detail, it becomes clear why Christianity fails to instill morality into its followers: with Christianity, acceptance of Christ is more important than moral behavior. That is an intrinsic moral flaw with Christianity and the reason why Christianity has a two thousand year history of violence and intolerance.