Because of Kamtza and Bar Kamtza, Jerusalem was destroyed.
It happened this way: A certain man had a friend named Kamtza and an enemy called Bar Kamtza. He once made a party and said to his servant, “Go and bring Kamtza.” The man went and brought Bar Kamtza.
When the man who gave the party found Bar Kamtza there he said, “See, you are my enemy; what are you doing here? Get out!” Said the other: “Since I am already here, let me stay, and I will pay you for whatever I eat and drink.”
Because of Kamtza and Bar Kamtza, Jerusalem was destroyed Said the host: “Absolutely not.”
“Then let me give you half the cost of the party.”
The host refused.
“Then let me pay for the whole party.”
Still the host refused, and took him by the hand and threw him out.
Said Bar Kamtza, “Since the Rabbis were sitting there and did not stop him, this shows that they agreed with him. I will go and inform against them to the government.”
He went and said to the emperor, “The Jews are rebelling against you.”
Said the emperor, “How can I know that this is true?”
“Send them an offering,” said Bar Kamtza, “and see whether they will offer it on the altar.”
So he sent with him a fine calf. While on the way he made a blemish on its upper lip (or as some say, on the white of its eye)—in a place where we count it a blemish but they do not.
“Because of the scrupulousness of Rabbi Zechariah, our House has been destroyed . . .” The rabbis were inclined to offer it in order not to offend the government. Said Rabbi Zechariah ben Avkulas to them: “People will say that blemished animals are offered on the altar.”
They then proposed to kill Bar Kamtza so that he should not go and inform against them, but Rabbi Zechariah ben Avkulas said to them, “Is one who makes a blemish on consecrated animals to be put to death?”
Rabbi Yochanan thereupon remarked: “Because of the scrupulousness of Rabbi Zechariah ben Avkulas our House has been destroyed, our Temple burnt, and we ourselves exiled from our land.” -Talmud, Gittin 55-56
The first half of the story I believe is known by everyone. The last section of the agadatah seems to not be repeated very often. How is this understood by the communities who seem to exault stringencies?