Sorry for the late reply. Been busy. I'll get to the point.
You may argue that the 'many nations' deserved to be massacred because their gods were demonic and required monstrous practices. This is hypocritical, however, because:
1. Yahweh was worshipped by the many nations (namely the Canaanites), and was a volcanic God related to metallurgy (hence why the OT often describes him in the terms of fire, rage and burning), similar to the Greek Hephaestus or Roman Vulcan.
2. Yahweh also required a horrifying practice: circumcision. Sure, it's better to cut you baby son's foreskin off than to burn him alive in the statue of Moloch, but circumcision is still very horrifying and it has medically been proven to cause significant trauma and permanent alterations to the brain (pic related). And Yahweh requires circumcision at as young age as only 8 days in Gen 17:12.
Secondly, not all gods were evil. Asherah, the mother godess of Canaan, is a good example. Yeah, the worshippers of Asherah practiced the so-called "sacred prostitution", but what is better: to have sex in the name of Asherah and Baal, or to cut your baby's foreskin off?
And Yahweh specifically asked for Asherah poles to be burnt down many times in Deut. This resulted in a lack of feminine figure in Abrahamic religions (where Christianity got a little better off with it's Virgin Mary, but not that much), which caused quite a few other problems, but that's a story for another days and irrelevant to our discussion. Back to the topic at hand.
Here's another passage I found. 2 Chronicles 15:13 "That whosoever would not seek the Lord God of Israel should be put to death, whether small or great, whether man or woman."
I had a dilemma as to whether to mention this passage or not, since 2 Chronicles is a historical book, not a part of the Pentateuch. In the end, I decided to include it because the rest of the chapter says that Asa gathered all of Judah and Benjamin, as well as the strangers from Ephraim, Manasseh and Simeon, and they have asworn with all their heart and soul, with loud voice, shouting, trumpets and cornets. An oath to which all of Judah rejoiced.
And after all this, I'd say that only one argument remains: "This all may be true, but these are the laws God gave to Israelites, not Christians". This is a very good argument, but also one which creates a great problem/incosistency. Which parts of the OT apply to Christians, and which do not, and why?
Reached the limit...again. To be continued...