This is not a convincing argument. All of us were chosen before the foundation of the world, long before we knew sin. (Ephesians 1:3-14)
Read Paul's own account of his conversion in Acts 22:
14 “Then he said: ‘The God of our ancestors has chosen you to know his will and to see the Righteous One and to hear words from his mouth. 15 You will be his witness to all people of what you have seen and heard. 16 And now what are you waiting for? Get up, be baptized and wash your sins away, calling on his name.’
Paul had been selected for sure, but he still had to have his sins WASHED AWAY.
Baptism was nothing but a symbolic gesture of a change in life. Only the blood of Christ can remove sin. Water merely gets you wet and shows lookers on that you mean it. Even the American Indians did it when adopting a stranger into their tribe, they would throw him in a creek to wash the old tribe off so he became a member of the new tribe.
And the Hindus still do it quite often. "even to them that believe on his name."