The Midrash here subtly points to the fact that Shimon and Levi could not truly claim to have been driven by fraternal loyalty if they were also capable of perpetrating a violent crime against their brother. One cannot claim to be driven by sincere, altruistic motives if he does not display the same passion and unwavering commitment to the ideal in question under all circumstances.
The Torah in Parashat Miketz tells of how Yosef, as the Egyptian vizier, cast baseless allegations against his brothers who had innocently come to purchase grain in Egypt, accusing them of coming to spy (“meragelim atem” – 42:9). The Torah does not explain the basis that Yosef contrived upon which he could make such claims, but we find in the Midrashim several descriptions of how Yosef tried to “verify” his unfounded suspicions. In one particularly poignant passage (Bereishit Rabba 91), the Midrash has Yosef telling his brothers, “I see in my [fortune-telling] goblet that two of view destroyed the large metropolis of Shekhem, and then you sold your brother to Arabs…” Yosef pointed to his brothers’ history of violence – from Shekhem to mekhirat Yosef – as cause for suspicion.
It is likely that Chazal here are not so much explaining how Yosef justified his allegations, as much as drawing our attention to these two events – the assault on Shekhem, and the sale of Yosef. In response to Yaakov’s condemnation of their assault on Shekhem, Shimon and Levi justified their violence by affirming their right and obligation to defend their sister’s honor: “Shall our sister be [treated] like a harlot?!” (34:31).
But any merit this argument may have had disappeared once they directed their violence toward their younger brother. The Midrash here subtly points to the fact that Shimon and Levi could not truly claim to have been driven by fraternal loyalty if they were also capable of perpetrating a violent crime against their brother. If their sense of devotion to family was so strong that it warranted killing the entire male population of a large city, then it would have been strong enough to enable them to accept Yosef’s preferred status in the family without seeking his elimination. Their violence against Yosef undermined whatever possible legitimacy they could have accorded to their violence against Shekhem.
Extreme measures taken in the name of idealism must past the test of consistency for it to be eligible for legitimacy. One cannot claim to be driven by sincere, altruistic motives if he does not display the same passion and unwavering commitment to the ideal in question under all circumstances. Chazal here criticize the brothers for bending the rules for the sake of their sister and then bending them again to turn against their brother. If we are passionately committed to “Dina,” we must be passionately committed to “Yosef.” We cannot invoke idealistic claims to justify extreme behavior unless we are prepared to make all sacrifices necessary to promote those ideals we claim to defend.