Weapons aren't good for protection tho. Ivar and the others were arguing that weapons would make them feel secure, however that's just not true. If the Lnu see the weapons, they'll think Thorfinn and the rest want to harm them and take their land. If anything, keeping weapons will just start an unneeded war. Instead, a treaty with the Lnu would make more sense, since both parties have been cooperating for quite a while now. I would've understood if Ivar wanted to hold on to guns from the start, but after such a long time of living and trading with the Lnu, it wouldn't make sense to arm yourselves.