Both Maimonides and Nachmanides agree that the people of Shechem were culpable. Rambam says one of the 7 Noachide laws is setting up a justice system to uphold law & order. Since the town did not bring Shechem to account for kidnapping Dina, all were liable for the death penalty (thus the pasuk referring to Shimon & Levi – BR. 49:6 – says "Hargu Ish," they killed a man; to a man, all were guilty). Ramban says, as idolators, they were subject to capital punishment. But if so, why did Yakov later criticize these sons, saying they resorted to a "craft of murder" more suitable to Esav? Commentators explain that Yakov was not angry so much at what they did, but rather how they did it. They should have acted outright, without subterfuge, either out of faith in their just cause to redeem Dina, or so as not to stigmatize Yakov as a deceiver. Note that Shimon & Levi were 13 years old at this time, & it is from this incident that the Midrash learns that a boy is obligated in Mitzvot at age 13! When asked why we should learn about Bar Mitzva from such a negative source, the Lubavitcher Rebbe commented: "This is not negative at all - quite the opposite! Shimon and Levi showed courage, heroism and devotion to their people by rescuing their sister! Would that ALL boys would be so admirable!