Those in the middle of the herd are protected. That's the situation of those of us in the "developed" world.

However, the herd has to have margins and existence for those at the edges is, by definition, marginal. They are vulnerable -- to predators, to stronger herd members who can steal their food and push them to the edge, to famine and drought and natural disasters.

The noble goal of morality is to improve life for everyone. But it's not possible for all members to be at the center of the herd. There will always be a margin and life at the margin will always have the possibility of breeding resentment and envy. Some will always have more status than others and may resent that and take violent action in response. Of course, the privileged ones will respond violently when/if they feel threatened.