As Saul, he was very zealous for his religion.
"And Saul was there, giving approval to his [Stephen's] death.
On that day a great persecution broke out against the church at Jerusalem, and all except the apostles were scattered throughout Judea and Samaria. Godly men buried Stephen and mourned deeply for him. But Saul began to destroy the church. Going from house to house, he dragged off men and women and put them in prison."
He thought he was doing what God wanted by destroying followers of Jesus.
Later, as Paul the Apostle, he was just as zealous, if not more so, for the Christian religion.
The only circumstance where you might say he didn't care for the Jews religion was when, as Paul the Christian Apostle, he disapproved of the Jews who refused to see Jesus as the Promised One, the Savior of all mankind.