Sforno on Genesis 34:27/ספורנו על בראשית ל״ד:כ״ז

1העיר אשר טמאו, unless according to the mores of Shechem (city) such behaviour was no longer considered despicable, Schechem would not have done what he did. He felt sure he could get away with it, as his townspeople would not object. However raping virgins was commonplace in Shechem already. They behaved in the manner described in Genesis 6,2 “they took women for themselves from wherever they chose.” [the punishment for this type of violence had been the deluge. Ed.]