The apostle Paul had no reason to hate Christians before he became one. Read that again, slowly.
Before his conversion, Paul's loathing of Christians was purely ideological. The only Christian we know he met face-to-face, pre-conversion, was Stephen, a man full of the Holy Spirit, wisdom, faith, and whose face was like that of an angel. But Paul hated him and all he represented. His hate was rooted in nationalism, dogmatism, chauvinism, and his own private demons.
No Christ-follower had hurt Paul personally. No one had given him grounds for such violent enmity. He was the original ISIS member. Then he became a Christian.
After that, he had many reasons, deeply personal ones, for despising other Christians: their pettiness, foolishness, meanness, gullibility. Paul's letters reveal how fractious, mulish, and small-minded Christians could be. But he loved them, lavishly. His love was rooted in grace, in his own story of divine love and how it found him, slayed him, raised him, made him ...1