I have made much of the argument for Christianity’s truth based on the moral argument. The basic idea of the moral argument is that atheism has no basing for objective morality; there is no reason for an atheist to be moral given their way of thinking about the world.
This form of argumentation is often miss-characterized by those in the vocal atheist movement. They say we are accusing them of being amoral, evil people who do not live lives that meet a high standard of right and wrong. Some web sites ever accuse us of saying atheists eat babies because they are so immoral. This is a fundamental misunderstanding of the argument.
In fact, the argument only works if most atheists are outwardly morally outstanding people. The idea is that a morally superior atheist has no objective basis for the moral life he or she is living. They are borrowing a set of moral absolutes from another worldview, unusually Christianity itself. A person only borrows a concept that he or she knows to be true at some level.
The atheist who is a fine, upstanding, and moral person proves by their very life that the atheist view of the world is inadequate. A better way to see the world is to admit there are moral absolutes established by a loving creator God. This is the only way to provide and intellectually tenable moral system (For a defense of that position by a professional defender of the Christian faith, see this book.).