Chazal teach us that the second Beis HaMikdash was destroyed because of sinas chinam - baseless hatred between man and his fellow man. Unlike the first Beis HaMikdash that was rebuilt after seventy years, the second Beis HaMikdash has still not been rebuilt after almost two thousand years. Why is it impossible for sinas chinam and the Beis HaMikdash to coexist?
The Rambam in Hilchos Beis Habechira, when discussing the purpose of the Beis HaMikdash, highlights its role in enabling us to perform the mitzvah of aliyah laregel, i.e. coming to the Beis HaMikdash on the shalosh regalim and offering special korbanos. There are korbanos offered in the Beis HaMikdash throughout the year, yet the Rambam emphasizes aliyah laregel as a primary purpose of the Beis HaMikdash. As such, Aliyah laregel can serve as a model to understand the essence of the Beis HaMikdash.
On yom tov, we conclude the mi shebeirach with the phrase, "v'yizkeh la'alos l'regel im kol Yistroel echav - May he merit to fulfill aliyah laregel together with the entire Jewish People." After the Brisker Rov once received an aliyah on yom tov the gabbai inadvertently omitted the words "im kol Yistroel echav" when reciting the mi shebeirach. The Brisker Rov then insisted that the mi shebeirach be repeated. Apparently the mitzvah of aliyah laregel cannot be performed as an individual; visiting the Beis HaMikdash on the shalosh regalim must be done as part of the Jewish People. This idea is expressed in Devarim - "b'vo kol Yisroel - when all the Jews come". The essence of aliyah laregel is Klal Yisroel coming, as a unit, to the Beis HaMikdash, and therefore the mi shebeirach must reflect this. Perhaps this is why the Rambam highlights aliyah laregel as a primary purpose for the Beis HaMikdash. The Beis HaMikdash is not just a place where an individual can offer korbanos to Hashem; it is the place of avodas tzibbur that enables the Jewish people as a whole to serve Hashem.
The notion of avodas tzibbur in contrast to avodas yachid appears to be a halachic principle that applies to many korbanos offered in the Beis HaMikdash. Specifically, Chazal raise the following concern: the communal korbanos of the omer, shtei halehcem, and lechem happanim, which were purchased with the funds raised through machatzitz hashekel, were made of flour and had the status of a korban mincha. A korban mincha that belongs to a kohein may not be eaten. Since the kohanim gave a machatzitz hashekel and thus have a share in these communal menachos, how were these menachos allowed to be eaten? This dilemma led some to believe that kohanim were in fact exempt from giving a machatzitz hashekel. However, we accept the view that kohanim are in fact obligated in machatzitz hashekel and therefore we are faced with this difficulty.
The permissibility of eating the aforementioned menachos presents a problem if one understands korbanos bought with communal (tzibbur) funds to be korbanos that belong to each and every individual that donated to the fund. The tzibbur, however, is not merely a group of individuals, but rather is a distinct entity called Klal Yisroel. As such, we need not be concerned that the kohanim's contribution to the machatzitz hashekel fund will render the menachos inedible, since the menachos did not belong to them as individuals, rather they belonged to Klal Yisroel as a distinct entity.
The idea of avodas tzibbur being distinct from a joint avodas hayachid of many individuals expresses itself in hilchos tefillah as well. Our tefillos are patterned after korbanos and we therefore have both tefillas yachid and tefillas tzibbur. The Rav, elaborating on the wording of the Rambam, develops the idea that chazoras hashatz is said as a form of avodas tzibbur. First we approach Hashem as individuals who are gathered together for our silent shemoneh esrei. We then follow with a tefillas hatzibbur that is reminiscent of the korban tamid which was purchased with the communal funds of machatzitz hashekel.
Recognizing that the Beis HaMikdash is the place of avodas tzibbur, we can understand why the presence of sinas chinam makes it impossible for the Beis HaMikdash to exist. A tzibbur can only be formed when there is love between the individual members who make up the tzibbur. As we mourn the destruction of the Beis HaMikdash, we are mourning the loss of the opportunity to serve Hashem as a tzibbur comprised of all of Klal Yisroel. May we succeed in overcoming the obstacle of sinas chinam, thus enabling us to once again offer korbanos tzibbur and merit the beracha, "v'yizkeh la'alos l'regel im kol Yistroel echav v'nomer amen."