There are exceptions because some known non agricultural societies (plains Indians) loved and relished killing their rivals.

But it feels like there is a subconscious want to war and commit violence by humans in general. And I think at least some of it stems from our apex predator origins. If the innate bloodlust was satiated less because the need to hunt was greatly reduced (via calories coming from agriculture), I could see that creating more of subconscious want to kill otherwise.