As he was approaching Damascus on this mission, a light from heaven suddenly shone down around him. He fell to the ground and heard a voice saying to him, “Saul! Saul! Why are you persecuting me?” “Who are you, lord?” Saul asked. Acts 9:3-5 (NLT)
Acts 8:1 says "Saul was one of the witnesses, and he agreed completely with the killing of Stephen." And later, in 8:3 it says "But Saul was going everywhere to destroy the church." This was Saul's job. The Bible doesn't say exactly why he felt this was his calling but we might assume he didn't like the new movement. Some of the beliefs were contrary to the Jewish traditions so many thought it was wrong.
Saul fought and fought for the cause he believed in. Then one day, on the road to Damascus he ran into Jesus, the Son of God. When Paul encountered the light of heaven and a Voice saying "Saul, why are you persecuting me?", what was his response? "Who are you?"
Saul was supposedly fighting for God but he didn't know who God was. Later in his life he regretted his actions and acknowledged the damage it did. How about you? Do you stand for something on behalf of God but don't know God himself? What are you fighting for? Better yet, who are you fighting for?