The perversion of the central Christian doctrines by religions who present themselves as Christians, but who reject the deity of Christ, the trinity, Christ's death and resurrection, the virgin birth, etc. That is the atrocity of the perversion of truth. But there are more. When a "Christian" group like some churches who picket funerals and spew hate and judgment come onto the scene, they are the antithesis of what Christianity should be and therefore give true Christians a bad name. And in centuries past Christian groups who murdered those who wouldn't convert were another example. Christianity has come a long way in realizing that atrocities do not win people to faith in Jesus Christ and that God did not condone these actions at all. You will know true Christians for their love for each other and most of all for Jesus Christ as their savior.