Sabbath Wars

Jesus was accused by the Pharisees of violating the 4th Commandment no fewer than 6 different times in the gospel records. Indeed, he had no sooner begun his public ministry by preaching in the synagogue at Nazareth on a Sabbath than the Jews filled with rage wanted to throw him off a cliff! Doesn't it seem strange that the emblem of peace and rest should be the occasion for such angry and violent conflict?