This is what law enforcement looks like in a voluntary society:

You can also check out Detroit Threat Management: https://reason.com/video/detroit-threat-management-anarchy-in-det/

I agree density is a problem, but I don't agree "human nature" demands only one approach. Often that term is just a catch all for an individual's lived experiences. If the be good, it be good. If they be bad, it be bad. We can build hyper-local systems which take into account density.

Comparing primitive cultures low on Maslow's Hierarchy without technology isn't a fair comparison.

Calling someone who sets up the initial rules a "ruler" isn't accurate. In a DAC, the rules can be changed at any time by the elected custodians. The initial rule set (the constitution) defines the community. This is open source, so anyone can create a different community if they want to change the rules but can't get support of the community that actually likes the rules as they are.

Enforcement can be done with code and smart contracts, not guns and violence. That's the key which changes everything.