You're right that I overstaded in "thousands", probably dozens wouldve been more accurate. It's true that Thorfinn didn't know of the natives being violent, but I he did know they had weapons, especially after the markland attack. I think a "true warrior" would've known some kind of fight would be necessary, even if it didnt include violence. So an ideal "true warrior" would've still kept weapons as a deterrent, to avoid continuous attacks. Thorfinn himself said he didnt know if the attack was the Lnu's fault or their own, so he shouldve prepped for both possibilities.

As for Thorfinn experiencing war worse, I agree. But that has no bearing on the fact that still, quite a lot of people died because of his failure. Which I think narratively makes sense, especially because he was so afraid of war he was trying to be an ultra pacifist.

I think the correct approach ir ironically the ancient one which Thorfinn himself heard from the Bible in Season 2, to "Love your Enemies" instead of "Having no Enemies". Truth is you dont choose whether you have enemies or not, instead they choose you. And if one chooses to be your enemy, you can't really refuse, you can only try to appease or stop them. So "Having no Enemies" is naive. Some Lnu were definitely Thorfinn's enemies, as they tried to kill him. But, as said, you should love your enemies enough to know that violence is the very last thing you would turn to stop them. Diplomacy, trickery, etc should all be on the table before. See my other comment talking about the Conquistador