The Sages tell us the story behind Emperor Nero's conviction that the Jews were rebelling against Rome. The nation had fallen to a low spiritual state characterized by baseless hatred. The story of Kamtza and Bar Kamtza was the pivotal event that ignited Nero's rage and caused the destruction of the Holy Temple:
"Because of Kamtza and Bar Kamtza, Jerusalem was destroyed." Gemara Gittin 55–56
Delivered by Rabbi Nachman Wilhelm of OnlineSmicha.com from Minneapolis M.N.