Others would claim they were the one-true-religion and that yours was "man-made."
Of course they can, but it doesn't make it so. We have the Truth, given to us as the Word of God, and we have faith given to us as a gift. Truth is not subjective, no matter what those who would lie, distort it to be. All liars have as their father the devil. All those who love the Truth, have as their Father, God.