Or HaChaim on Genesis 34:7/אור החיים על בראשית ל״ד:ז׳

1 ויעצבו…כי נבלה עשה בישראל. They were distressed… because he had committed a disgraceful act against Israel, etc. The Torah uses two expressions, 1) "they were angry," and 2) "they were distressed" to indicate that Shechem had been guilty of two wrongs. It would have been shameful for the family of Jacob even if Shechem had married Dinah, seeing that they would not give their sister to an "unclean" person. However, that would have been merely distressing. The fact that Shechem had raped their sister, something that was repugnant even to the local inhabitants, i.e. וכן לא יעשה, aroused their anger. Bereshit Rabbah 80,6 states that the Gentiles had accepted sexual restrictions upon themselves after the deluge. This included rape.