The gemarah in gittin (58a) describes a story wherein a carpenter's apprentice manipulates a series of unfortunate events (for the carpenter) which end up with the carpenter's wife now married to the apprentice and the carpenter, who is stuck paying off her huge kesuba, is forced to work off the money he owes his former apprentice by being a servant to the new happy couple. The gemarah describes how his tears mix with the drink he is serving and because of that the decree of the destruction of the temple is sealed.
It's a sad story. But what was so significant about this particular story that this one incident sealed the decree? Why would the entire Jewish people be punished for millennia for what was, at worst, an isolated case of adultery?