God is documented as being rather keen on genocidal smiting. That is part of the exact problem. I googled two relevant examples:
1: God commands King Saul: attack the Amalekites and totally destroy all that belongs to them. Do not spare them; put to death men and women, children and infants
2: When the Israelites entered the Promised Land, they were often commanded to carry out total destruction against the Canaanite nations. "they utterly destroyed all that was in the city, both man and woman, young and old, and ox, and sheep, and ass"
I'm not into religion, but it has had a massive influence on my culture (NZ) so I pay some attention to it.
Holy books seem to be buffets that people just pick their favorite dishes from, for the most part. At least, in the western world. I can't speak to elsewhere.
1. While approaching the land, the Amalekites had attacked them, preying on the weak. God had said that they would be destroyed. Now, probably partly as a test for their first king (he failed, didn’t eradicate them), God said, get on and do it.
2. God had promised the land to Abraham and his descendants, but said they’d only get it in four hundred years’ time, because “the iniquity of the Amorites is not yet complete”—they still had time to choose God’s ways. Only once they were irredeemable were they to be destroyed.
Lots of people who claim to be Christian still quote Leviticus as justification.
Not all of it, banning mixed fabrics (19:19) and having land ownership revert every 50 years including houses outside walled cities (25:31) and animal sacrifice (all of chapters 1 and 3) would reveal how disconnected such people are, possibly even to the speakers themselves, so it has to be selective.
All I'm saying is, I could see how someone who believes Satan influences the world would come to that idea.