What is the comparison to Adam?
Rashi: They are like Adam ha'Rishon (refer to 6:7:2:1).
Radak: They are like a man who betrays his friend and transgresses his Bris. So it was light in their eyes to transgress My Bris.
Radak citing Targum Yonasan: They are like earlier generations.
Why does it say "Avru Bris"?
Refer to 6:7:1:2.
Malbim: There are two times that Malchei Yisrael killed Nevi'im. (a) Izevel killed Nevi'ei Hashem; they were Talmidim of Eliyahu, who was from Binyamin. After Pilegesh b'Giv'ah, the remnant of Binyamin married women of Yavesh Gil'ad, and settled there 1 . Surely, they were killed in Gil'ad. (b) When Yaravam became king, he made Shechem (which was an Ir Miklat of the Leviyim) his capitol. Surely Nevi'im there rebuked him for making the calves, and he killed them. The Navi compares killing Nevi'im in Gil'ad and Shechem to other killings in these places amidst Kin'as Hashem over Zenus. (a) Bnei Yisrael killed Anshei Yavesh Gil'ad for transgressing the Bris and Cherem upon those who will not come to avenge the Zenus (Pilegesh) in Giv'ah. (b) Bnei Yakov killed Anshei Shechem due to the Nevalah done to Bas Yakov. In contrast, now they killed Nevi'im amidst Kin'ah for the calves and Ba'alim, which the Nevi'im scorned, as if it is the Kin'ah of Zenus in earlier days! Hemah (the Nevi'im) appeared to [those who killed them] like one who transgressed the Bris (to fight, in the days of Pilegesh b'Giv'ah).
Why would they settle there? Even if many of the 400 women inherited from their fathers (since all the men of Yavesh Gil'ad were killed), the 600 survivors of Binyamin inherited Binyamin's entire portion, which was proper for 45,000 men (Bamidbar 26:41)! (PF)
Where did they betray Hashem?
Rashi (from Bereishis Rabah 19:18): In the good land in which I settled them. This is like Adam ? I entered him into Gan Eden, and he transgressed My Mitzvah!
Radak: In the place where I influenced good on them.
