If talking no jutsu are working against this Neandhertals people, Taiga may already used it at their first encounter. But nope, it didn't work. The moment Neandhertals met someone outside their tribe, their axe do the talking, not their mouth. That's why, it really cannot be help. That primitive era demand kill or to be killed.
Beside, it's killing for survival, not killing for joy like a psychopath. That's two different things.