I think there probably are civilizations so evil that warfare is justified against them. The Nazis certainly were. The evidence we have, both scriptural and archaeological, is that at least some of the Israelite’s enemies practiced infant sacrifice to their idols and tried to traduce the Jews into doing the same. (Yes, I know - who are we to talk?)
The Canaanite cultures seemed to practice some very evil traditions. The Canaanite textual and archaeological evidence supports the argument that the Canaanites condoned and practiced child sacrifice, temple prostitution, child sexual abuse, incest, bestiality, and homosexuality. Furthermore, these were not isolated, antisocial practices, but were condoned and supported by their idolatrous religious practices, and were themselves modeled on the acts supposedly conducted by their gods.
Incestuous acts were condoned by the actions of the Canaanite elder god El, who had 70 children by Asherah, including Baal and his sister Anat, with whom Baal had sex. Asherah tried to seduce Baal, and told El, who encouraged him to have sex with Asherah to humiliate her. Baal also had sex with his daughter Pidray. These actions are not presented to the Canaanites in a negative manner. (For Canaanite texts relating these tales, see W.F. Albright, Yahweh and the Gods of Canaan: A Historical Analysis of Two Contrasting Faiths (Winona Lake, IN: Eisenbrauns, 1968, and “El, Ashteru and the Storm-god,” translated by Albrecht Goetze, in The Ancient Near East: Supplementary Texts and Pictures Relating to the Old Testament, edited by James B. Pritchard, (Princeton: Princeton University Press, 1969))
Incest was initially punished by the Canaanites by death or banishment, but after the 14th century B.C., the punishment for incest had been decriminalized and reduced to a simple fine. Harry A. Hoffner Jr. (in “Incest, Sodomy and Bestiality in the Ancient Near East” in Orient and Occident: Essays Presented to Cyrus H. Gordon on the Occasion of his Sixty-Fifth Birthday, edited by Hoffner [Germany: Neukirchen Vluyn, 1973)), in describing the gradual decriminalization of the incest taboo, describes relevant Hittite tablets which contain rituals to remove the impurity of incest and bestiality from a man, which would allow a man to remain in his city despite being incestuous, indicating that such practices were common enough to generate recorded rituals to remove the societal onus.
The use of temples to practice prostitution, both heterosexual and homosexual (and to benefit the religious priests monetarily) was common among the Canaanites (For textual cites, see Jonathan N. Tubb, *The Canaanites (Norman, OK: University of Oklahoma Press, 1998) who cites texts from Ugarit which describes Anana’s cult as involving members of the aristocratic priestly sect and both male and female temple prostitutes. Walter Hinz, in The Cambridge Ancient History: History of the Middle East, 3rd ed (ed. by I.E.S. Edwards, C.J. Gadd, and N.J.L. Hammons (London: Cambridge University Press, 1971), states “From the very earliest days numerous priests with the servants were attached to the temple buildings in the Acropolis of Susa. Apparently these performed their ceremonies naked, to judge by Elamite seals and several small finds from stratum D at Susa onwards - that is before the time of the Akkadan Empire.” John Gray, in *The Legacy of Canaan: The Ras Shamra Texts and Their Relevance to the Old Testament *(Leiden, Netherlands: E.J. Brill, 1965) cites a Canaanite liturgical text which seems to indicate that after the story of El having sex with two goddesses was told, the incident was reenacted as a fertility rite: “To be repeated five times by the company and the singers of the assembly.”