However, considering that the people during the Second Temple period were engaged in Torah study, observance of mitzvot, and acts of kindness, and that they did not perform the sinful acts that were performed in the First Temple, why was the Second Temple destroyed? It was destroyed due to the fact that there was wanton hatred (sinat chinam) during that period. This comes to teach you that the sin of wanton hatred is equivalent to the three severe transgressions: Idol worship, forbidden sexual relations and bloodshed.
אֲמַר לֵיהּ: לָא. אֲמַר לֵיהּ: יָהֵיבְנָא לָךְ דְּמֵי פַּלְגָא דִּסְעוֹדְתָּיךְ! אֲמַר לֵיהּ: לָא. אֲמַר לֵיהּ: יָהֵיבְנָא לָךְ דְּמֵי כּוּלַּהּ סְעוֹדְתָּיךְ! אֲמַר לֵיהּ: לָא. נַקְטֵיהּ בִּידֵיהּ וְאוֹקְמֵיהּ וְאַפְּקֵיהּ. אָמַר: הוֹאִיל וַהֲווֹ יָתְבִי רַבָּנַן וְלָא מַחוֹ בֵּיהּ, שְׁמַע מִינַּהּ קָא נִיחָא לְהוּ, אֵיזִיל אֵיכוֹל בְּהוּ קוּרְצָא בֵּי מַלְכָּא. אֲזַל אֲמַר לֵיהּ לְקֵיסָר: מְרַדוּ בָּךְ יְהוּדָאֵי!
The host said to him: No, you must leave. Bar Kamtza said to him: I will give you money for half of the feast; just do not send me away. The host said to him: No, you must leave. Bar Kamtza then said to him: I will give you money for the entire feast; just let me stay. The host said to him: No, you must leave. Finally, the host took bar Kamtza by his hand, stood him up, and took him out. After having been cast out from the feast, bar Kamtza said to himself: Since the Sages were sitting there and did not protest the actions of the host, although they saw how he humiliated me, learn from it that they were content with what he did. I will therefore go and inform [eikhul kurtza] against them to the king. He went and said to the emperor: The Jews have rebelled against you.
אֲמַר לֵיהּ: מִי יֵימַר? אֲמַר לֵיהּ: שַׁדַּר לְהוּ קוּרְבָּנָא, חָזֵית אִי מַקְרְבִין לֵיהּ. אֲזַל שַׁדַּר בִּידֵיהּ עִגְלָא תִּלְתָּא. בַּהֲדֵי דְּקָאָתֵי שְׁדָא בֵּיהּ מוּמָא בְּנִיב שְׂפָתַיִם, וְאָמְרִי לַהּ בְּדוּקִּין שֶׁבָּעַיִן – דּוּכְתָּא דִּלְדִידַן הָוֵה מוּמָא, וּלְדִידְהוּ לָאו מוּמָא הוּא. סְבוּר רַבָּנַן לְקָרוֹבֵיהּ מִשּׁוּם שְׁלוֹם מַלְכוּת. אֲמַר לְהוּ רַבִּי זְכַרְיָה בֶּן אַבְקוּלָס: יֹאמְרוּ בַּעֲלֵי מוּמִין קְרֵיבִין לְגַבֵּי מִזְבֵּחַ! סְבוּר לְמִיקְטְלֵיהּ דְּלָא לֵיזִיל וְלֵימָא. אֲמַר לְהוּ רַבִּי זְכַרְיָה: יֹאמְרוּ מֵטִיל מוּם בַּקֳּדָשִׁים יֵהָרֵג! אָמַר רַבִּי יוֹחָנָן: עִנְוְותָנוּתוֹ שֶׁל רַבִּי זְכַרְיָה בֶּן אַבְקוּלָס, הֶחְרִיבָה אֶת בֵּיתֵנוּ, וְשָׂרְפָה אֶת הֵיכָלֵנוּ, וְהִגְלִיתָנוּ מֵאַרְצֵנוּ.
The emperor said to him: Who says that this is the case? Bar Kamtza said to him: Go and test them; send them an offering to be brought in honor of the government, and see whether they will sacrifice it. The emperor went and sent with him a choice three-year-old calf. While bar Kamtza was coming with the calf to the Temple, he made a blemish on the calf’s upper lip. And some say he made the blemish on its eyelids, a place where according to us, i.e., halakha, it is a blemish, but according to them, gentile rules for their offerings, it is not a blemish. Therefore, when bar Kamtza brought the animal to the Temple, the priests would not sacrifice it on the altar since it was blemished, but they also could not explain this satisfactorily to the gentile authorities, who did not consider it to be blemished. The blemish notwithstanding, the Sages thought to sacrifice the animal as an offering due to the imperative to maintain peace with the government. Rabbi Zekharya ben Avkolas said to them: If the priests do that, people will say that blemished animals may be sacrificed as offerings on the altar. The Sages said: If we do not sacrifice it, then we must prevent bar Kamtza from reporting this to the emperor. The Sages thought to kill him so that he would not go and speak against them. Rabbi Zekharya said to them: If you kill him, people will say that one who makes a blemish on sacrificial animals is to be killed. As a result, they did nothing, bar Kamtza’s slander was accepted by the authorities, and consequently the war between the Jews and the Romans began. Rabbi Yoḥanan says: The excessive humility of Rabbi Zekharya ben Avkolas destroyed our Temple, burned our Sanctuary, and exiled us from our land.
To conclude the story of Kamtza and bar Kamtza and the destruction of Jerusalem, the Gemara cites a baraita. It is taught: Rabbi Elazar says: Come and see how great is the power of shame, for the Holy One, Blessed be God, assisted bar Kamtza, who had been humiliated, and due to this humiliation and shame God destroyed God's Temple and burned God's Sanctuary.
Yair Rosenberg, Other People’s Sin’at Chinam, Tablet Magazine, July 2013
What’s striking about this tale is that it apportions blames to the people recounting it, namely, the rabbis who did not intervene at the party. The host of the affair, the ostensible culprit, is never even named. While the Talmudic sages could easily have pinned the entire episode on him, they chose instead to share the blame themselves. National tragedy, in the traditional understanding, is not an opportunity to assert our own sense of superiority, but to foster a spirit of self-critique. As the Mussaf prayer every Rosh Chodesh reminds us, “because of our sins, we were exiled from our land.”
On Tisha B’Av, of all days, we are not meant to point to flaws outside ourselves, however apparent they may be, but rather to examine those within. After all, we can never truly know the minds and motivations of others. The only baseless hatred we can diagnose is our own.