Ummm...I'm not sure where you're getting this view of Paul, because it sure isn't in the Scriptures.
"I am a Jew, born in Tarsus of Cilicia, but brought up in this city, educated under Gamaliel, strictly according to the law of our fathers, being zealous for God just as you all are today." ~quote of Paul in Acts 22:3
"Paul began crying out in the Council, 'Brethren, I am a Pharisee, a son of Pharisees; I am on trial for the hope and resurrection of the dead!'"~Acts 23:6
"So then, all Jews know my manner of life from my youth up, which from the beginning was spent among my own nation and at Jerusalem; since they have known about me for a long time, if they are willing to testify, that I lived as a Pharisee according to the strictest sect of our religion." ~quote of Paul in Acts 26:4-5