I think Thorfinn is being quite realistic in the terms of inside Vinland saga. Practically every Lnu wants peace except Miskwekepu’j, and he just went and attacked Thorfinn. Ivar used his sword which wasn’t good, even though Thorfinn told him not to as he was going to De-escalate the situation himself.
Basically the nords are being paranoid, and by trying to prevent the future he saw, Miskwekepu’j is gonna cause it