Why Differ on the Source of Principles and Values?

Christians often imply that only Christians can have principles and values, and that a "relationship with God" is essential for overcoming "original and enduring" evil. As long as this attitude prevails, that Christians are right and everyone else is wrong, how can there ever be peace and harmony? How is this any different than the Muslim belief of the same ilk? Must we all become either 100% Christian or 100% Muslim in order to get along?
What is the likelihood of that ever happening? There have always been, and always will be, non-believers. Does this mean that we will forever be burning heretics at the stake and beheading infidels?

There is another possibility if only we will consider it. It is the one suggested by Sam Harris in his book "The End of Faith". If we Christians, Jews, Muslims, Hindus, etc. can turn loose of our religious dogma, then maybe we will discover that there are more useful and constructive values upon which we can all agree. e.g. respect, goodwill, compassion, liberty, and that these things must be mutual if we are to live in peace. These values derive from common sense. They do not need any supreme authority, whether God or church, to impose them upon us. To claim that they do sets up a mechanism by which we dehumanize those who disagree and allows us to label them as evil itself, thus justifying any means we are capable of inventing to destroy them.

Evil is not some monster which controls us. Evil is when we lose sight of our connectedness with each other. It is when we lose awareness that when one person's freedom is denied, all freedom is in jeopardy. Evil is when one religious group tries to force its ideas on others of a different persuasion, and this usually happens because we have been taught that we have "the word of God" in a book. Here's hoping we learn better before it is too late.