There are two basic ways to influence behavior; you can use/threaten force or you can persuade. The taxers think that persuasion is insufficient encouragement in many cases to get people to contribute to public goods. I think this ignores shame. Shaming has been regarded particularly by leftists as an unethical tactic, even if used for socially beneficial ends, but that actually depends on what you compare it to. Compared to coercion, shaming reduces violence and carries lower social costs.

There is no reason to assume that a completely voluntary society would have any less competition for social status than our present society. By imposing status costs on free riders and rewarding status to contributors, there is every reason to expect that the net level of public goods would be just as high if not higher without a monopoly government. The difference would be in how those goods were administered and their composition. Contributors would have much more control over how their contributions were distributed with a result of more efficient administration.

Competition is the force that turned single-celled organisms into vertebrates, turned apes into engineers. Sanction against violence is what differentiates civilized societies from savages and barbarians. An optimized civil society is one where competition among members is encouraged in socially beneficial ways and discouraged with regards to initiatory violence.