Why was Saul of Tarsus so angry about Jesus and His followers?
Saul of Tarsus was infuriated because he was defending his religion. As a Pharisee and key member of the Sanhedrin, hearing about Jesus' miracles and seeing more Jews follow the Messiah from Nazareth provoked him deeply. His anger stemmed from defending his religious system, not merely personal offense.
Les explains that Saul of Tarsus was a Pharisee of the Pharisees and one of the key men of the Sanhedrin, likely in his 30s and almost the same age as Jesus. When Saul heard about the miracles Jesus of Nazareth performed and learned that more Jews were following the Messiah from Nazareth, it totally infuriated him. Les says Saul was defending his religion; first he had to defend his religion, and then he had to defend his apostleship. He had a lifetime of fighting.