I like what this blogger has to say about Tisha B'Av:
The people of Israel crucified the Lord of life -- who disagreed with their verdict so passionately that He overturned it by rising from the dead. Jesus was right. The Jews were wrong. And still are, til this day.So, they do well to mourn the loss of their temple, and to ponder the reasons thereof. May God grant that, as time moves on, an ever-growing number of the Jewish people will find in the Messiah they spurned the true Sacrifice, and the ultimate Temple.