(א) הכתוב אומר כו'. אך קשה אם שכם חטא כל העיר מה חטאו להרוג???... ונראה דלא קשיא מידי, משום דלא דמי שני אומות, כגון בני ישראל וכנעניים, שהם שני אומות, כדכתיב (פסוק טז) "והיינו לעם אחד" – ומתחלה לא נחשבו לעם אחד, ולפיכך הותר להם ללחום כדין אומה שבא ללחום על אומה אחרת, שהתירה התורה.
(1) ... This is difficult: If [only] Shechem sinned, what was the sin of the [rest of the] city [for which they deserved] to die?... It appears that there is no difficulty [explaining why all the males in Shechem deserved to die], because [a war between] two nations is different. The Jewish people and the Canaanites are considered two nations, as it is written “and we will be one nation” (Bereishit 34:16), [implying that] initially they were not considered one nation. Therefore they were permitted to fight, like any nation who fights another nation, which the Torah permits.
Yakov clearly disagreed with them, although Gur Aryeh does not write what Yakov's arguement back to them was, what might we suggest to be Yakov's counter to them based on the Gur Aryeh's approach??
We will use the next three sources to try and find proof to either Yakov or to his sons:
(א) אשר ברכו. לישראל: (ב) ברוך עמי. ישראל אשר בחרתי לי לעם בהיותם במצרים:
(1) Which...blessed them [lit. him,] i.e., Israel. (2) Blessed is My people Yisrael, that I chose for Myself as a Nation when they were in Egypt.
(7) And ה' continued, “I have seen the degradation of My Nation in Egypt, and have listened to them cry because of their taskmasters; yes, I am mindful of their suffering.