Seven transgressions were committed by Israel on that day [of the Destruction of the Temple]: they killed a priest, a prophet, a judge, they shed innocent blood, they profaned the Divine Name, they defiled the Temple Court, and all this was done on Shabbat which was also Yom Kippur. (Lamentations Rabbah, Proems 23)
This midrash strikes me as ludicrous. It is difficult to imagine it being delivered in a serious tone, though, given its place in Lamentations Rabbah, it probably was. To a modern sensibility, however, it reads like a tabloid: over the top and giddy, with details of depravity.
The number seven is of interest here; that symbolic number of Sabbaths and sabbaticals and jubilees. Seven weeks before Pesah is Shabbat Shekalim. Seven weeks before Shavuot is Pesah. Seven weeks before Rosh Hashanah is where we are now: Tisha b'Av. The calendar gives us these Jewish connection points at seven day/week/year intervals, each one a spiritual opportunity. With Tisha b'Av, we are connected via the "seven" of the calendar to the Season of Repentance and via the midrash to the idea of our own sinfulness. As Rabbi Alan Lew (z"l) wrote:
Exactly seven weeks before Rosh Hashanah, we mark the turn toward Teshuvah—repentance or return—with the observance of Tisha b'Av. Tisha b'Av is the beginning of Teshuvah, the point of turning toward this process by turning toward a recognition of our estrangement from God, from ourselves, and from others. (This is Real and You Are Completely Unprepared, 2003, p. 52)
So maybe the midrash is not so ludicrous: it invites us to connect calamity with our own actions, not because we believe in a God who strikes us and our temples down with lighting rods of anger over our wrongdoing (as the midrash taken at face value would suggest), but because the Jewish holiday cycle is ushering us into a seven-week period of reflection. Or as Rabbi Lew puts it: "The time between Tisha b'Av and Yom Kippur, this great seven-week period of turning, is the time between the destruction of Jerusalem—the crumbling of the walls of the Great Temple—and our own moral and spiritual reconstruction" (p. 53). We will begin with fasting next week on Tisha b'Av and end with fasting eight weeks later on Yom Kippur. May we merit repenting, forgiving, and rebuilding our inner selves in a way that earns us sevenfold praise.