There are zillions of instances throughout history where "Christians" have done horrible things in the name of Christ. Christians everyday commit sins and crimes. This however does not mean that Christianity justifies their actions. It, however, does the opposite and stand in opposition to sinful actions. Christ taught us things like love our enemies, do good to those who hate us. But humans are sinful and will do things their way. Humans will use anything to justify their actions, unfortunately Christianity has been the flag for many terrible actions. Just because someone claims to be a Christian doesn't mean that what they do is what Christ stood for. Its one thing to call yourself a Christian and to live as a Christian should.