Whatever the reason for Ya’akov’s disapproval of Shimon and Levi’s actions (see Friday’s post), one thing we can say: his reaction is incredibly muted. Rashi interprets "achartem osi" as meaning no more than "you disturbed my concentration" and took me away from my avodah -- hardly an expression of anger. Contrast that with Ya’akov’s words to Shimon and Levi in Parshas VaYechi, where he lets them have it, telling them, "Klei chamas m’cheiroseihem," (49:5) that they stole the tools of Eisav (see Rashi) in order to commit murder. Why the change in attitude? Why the harsh reaction to what earlier had passed by with no more than mild criticism?
Rashi writes that the Torah stresses that Shimon and Levi were "achei Dinah" to give them credit for putting their necks on the line to stick up for their sister. The Midrash, however, gives us a different perspective: "achei Dinah -- v’lo achei Yosef."
At the time Shimon and Levi went to battle with Shchem, they claimed they were acting only to protect Dinah -- a noble expression of brotherly love. Fast forward to the events of our parsha and it is Shimon and Levi who act as ring leaders in the effort to get rid of Yosef. "Shimon v’Levi achim" (49:5) – united in their desire to do their brother in (see Rashi ibid).
R’ Shaul Yisrael (printed in Siach Shaul al haTorah) explains that at the time the fight with Shchem, Ya’akov had to give Shimon and Levi the benefit of the doubt and he could not impugn their motives. However, in retrospect, after what they did to Yosef, that was no longer the case. Brotherly love cannot serve as the justification for battle with Shchem when that same brotherly love is so easily pushed aside when it came to dealing with Yosef. Shimon and Levi's own behavior called their actions and motives into question and gave Ya’akov cause for his harsh words later in life.