Here is my, from the top of my head, by no means an expert's comprarisson and parralel to what happened in Canaan...
-what do we know about the events and mistreatments that were taking place in that society? didn't they force their own women into prostitution (idk if it's bad enough for you tho (tr) :-D ) and sacrified their own children to their gods...don't we today go to wars with nations based on moral reasons - mistreating their own people, comitting atrocities?...and when we do (go to wars with other nations), don't inocent people get killed too?
idk...I can ask the jewish take on the event if you want, but it was thousands of years ago, standards and practices have changed a lot, even compared to 100 years ago...so just because it's in the Bible it's difficult for us to grasp...