I think our difference in opinion comes down to your higher tolerance for coercion.

Do you really? I hope not.

I shouldn't assume that this is the entire reason for our difference in opinion. But I do think that you (like most people I talk to, and like myself in the past) oppose coercion in principle, but often overlook it in practice. Many people do not even find the word applicable to most government behavior, having accepted some idea of a social contract.

Sam has a problem. He has a number of very poor nephews and nieces. He has been working with a charity organization to help them, but the organization needs more funding. So Sam goes out and starts demanding money from his neighbors to give to the charity group. If anyone refuses to contribute, Sam kidnaps that person and locks them in a cage.

It's not my place to convince you that you, or other people, are being coerced if you do not feel put upon. Maybe it isn't coercion if you don't object. And I don't intend to whine about myself as a victim; I am fortunate and comfortable and so far no one has thrown a flashbang grenade into my child's crib.

Here you have outlined a position stating that efforts at consistency in social theory leads to harm. I would dispute that the choice of, say, communism vs. democratic capitalism matters less to human welfare than the circumstance of how consistently the ideals of each model are applied. Of course, if you make enough of the right exceptions, you will get better results. How do you get the right exceptions? You can leave it to luck, but that doesn't inspire confidence. The alternative is to rely on carefully-thought-out policies for being advantageously flexible. In other words, another textbook political theory.

Though the moral and political issues are important, I prefer a more scientific approach of discussing practical, measurable indications of success in specific areas.

You assert one:

governments are demonstrably better agents of policing than NGOs

Are you sure?

If you believe this, and it is not simply a matter of faith, you must have evidence for your belief. We have plenty of data about how policing in the United States works. You could argue that the bad examples are notorious exceptions to the norm, which is good enough to excuse some amount of misbehavior. But you go farther, asserting that the police we have are better than Brand X.

Government enforces a strict monopoly on most police activity, so it's hard to imagine what the alternative might look like, much less demonstrate that it is inferior. No doubt, there would be abuses. In my preferred dystopia, "Law enforcement agents will take advantage of their authority, abusing innocent people, and victims will face an uphill battle seeking redress. Now and then an especially outrageous case will lead to a large settlement for the victim, but do you think the law enforcement company will be shut down? Of course not; it will be a simple matter of apologizing to the community, implementing better training and standards, and reassuring investors and customers that the mishap won't happen again. Only the most abusive, incompetent, and corrupt law enforcement companies would ever be forced out of business."

The few glimpses we have of private policing are not exactly suggestive of Abu Ghraib, e.g. Paid Private Security in Oakland, CA.

Probably the biggest fear is that commercial cops will give better service to wealthier communities and poor folks will get the shaft. (This image is not so very hard to imagine, for some reason.) Do you feel that T-Mobile, Amazon, and Wal-Mart give unacceptable service to poor customers? Do you think destitute people get much benefit as free riders (not quite free, they pay taxes too) today? Would they not benefit from commercial police services provided to their less-poor neighbors? Would they appreciate having a no-frills 911 option over a no-answer 911, or worse?

If Brand X plausibly led to our country having 23.4% of the world's prisoners, many of them locked up for drug offenses widely perceived as unjustified, I would expect you to claim immediate victory in the argument.