"...All have sinned, and come short of the glory of God" (The Bible, New Testament, Epistle to Romans, chapter 3, verse 23). The Holy Scripture condemns fallen humanity without any exception: "The best of them is like a briar; the most upright is sharper than a hedge of thorns..." (The Bible, Old Testament, Book of the prophet Micah, chapter 7, verse 4). Furthermore, even children are affected with the rottenness of sin: "The wicked are estranged from the womb: they go astray as soon as they be born, speaking lies" (The Bible, Old Testament, Psalms, chapter 58, verse 3).
Of course, we should not have placed hardened sinners, on the way of whom is "destruction and misery" (The Bible, New Testament, Epistle to Romans, chapter 3, verse 16), on the same footing as infants who have just started their lives, if sin was the presence of some negative action in a person's life. But sin is first of all a lack of positive origin in our life, absence of Stable Heavenly Foundation, and if we are trying to build something on this planet without that foundation - whether it be a house or relations with our neighbors - it will collapse sooner or later.
Fortunately, the curse that fell upon humanity through disobedience of Adam and Eve was removed already almost two thousand years ago thanks to the redeeming sacrifice of Jesus Christ: "...God was in Christ reconciling the world to Himself, not imputing their trespasses to them, and putting the word of reconciliation in us. Then we are ambassadors on behalf of Christ, as God exhorting through us, we beseech you on behalf of Christ, be reconciled to God. For He has made Him who knew no sin, to be sin for us, that we might become the righteousness of God in Him" (The Bible, New Testament, 2 Epistle to Corinthians, chapter 5, verses 19-21).
However, there are people who are sincerely confident of their sinlessness: they neither killed anyone nor did they steal or commit adultery. But Omniscient God judges not only deeds but also thoughts. "If we say that we have no sin, we deceive ourselves, and the truth is not in us. If we confess our sins, He is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness" (The Bible, New Testament, 1 Epistle of John, chapter 1, verses 8-9).