Is the gospel according to David and Jesus different?

David prayed for God to break the teeth of the wicked, and Jesus taught us to love our enemies. Why is the gospel according to David and Jesus different? Did David get it wrong? God said that David could not build his temple because of the blood on his hands. Are we making a mistake when we practice David's type of aggressive religion instead of the religion of peace, forgiveness and nonviolence taught by Jesus, Gandhi, and Martin Luther King Jr.?