It's a theory that in reality already mostly doesn't exist. You can hire a range of body guards, personal security people, bounty hunters, and self-proclaimed bad asses to fuck people up.
...the more money you have the more connected you are, the more stuff like that you can do.
NAP is a theory that requires people with money "respect" rather than chilling in the forts they've already built in this system, let alone a more free market one.
NAP is a pipedream Libertarians have circle jerks about but like most of their theories would be utter vaporware in practice.