It may seem strange that the Sages named sinat chinam, "baseless hatred," as the explanation for the destruction of the Second Beit HaMikdash. It relates to the story in which Bar Kamtza was mistakenly invited to a feast instead of Kamtza, and was thrown out when the mistake was realized. Bar Kamtza was so enraged against the community and its rabbis that he devised a plot to make Caesar believe that the Jews were revolting and would attack them. But the hatred there was not baseless at all. Bar Kamtza was forcibly removed from the party, undergoing great personal embarrassment, and had good reason to hate all those who were present and did not object!