Why do we have to be nice those who are nasty?

One of my biggest struggles in life is being nice to those who don't deserve it. I'm fairly good at ignoring them and pretending they don't exist. But when I am forced to interact with those so clearly controlled by the powers of this world; the selfish, hateful, self-serving, back-stabbing... well, you get the idea. Returning kindness for hatefulness feels to me like rewarding their bad behavior. It feels like weakness to me. I am a fighter by birth, nature, and culture. I was raised to think independently, to defend myself and those I love from injustice and unfairness. We Walkers are the first to give each other a hard time, but when "outsiders" come at us, we are a cohesive force with which to be reckoned. So, as a Christian, I understand all of the Scriptural admonitions to treat others with love and compassion. I understand about giving someone my cloak when they ask for my shirt. I understand about going a mile when forced to go half a mile. I get all that, I do. But when I am not being persecuted FOR my faith, but in spite of it, simply because I allow it in an attempt to be the bigger person... It's hard to swallow. And I have to wonder, am I helping this person? Is my apparent acceptance of her hatefulness and downright meanness reinforcing her bad behavior? I feel it is. When I confront her and draw my line in the sand, I am free of her nastiness for a short period. But because I choose not to be confrontational on a daily basis, I (and many around me) endure her tirades,tantrums, and hatefulness. I just don't see how this is for the greater good. Jesus confronted those who were wrong, did he not? I'm not so sure it's Christ-like to see someone on a daily basis so blatantly mistreating others and cheating the system and not take any action at all. Is it wrong to pray for her to find work elsewhere so she can torture someone else?