Earlier quoted context omitted.
I don't think it's so subjective. If a democratic government decided that policing, clean air or firefighting weren't public goods they'd be incorrect. Even if polling supported it.
Anarcho-capitalists would argue strongly that all 3 of your examples are no different from any other service provided to customers. I've seen them (or sympathetic sci-fi writers) think up all sorts of imaginative scenarios about how that might work. Personally I agree with you, I think privatizing any of those things would be madness, because the real world never ends up working like the ideological fantasy, but it's…
That's just silly, we've had the anarcho-capitalists perspective in the past, that's how the modern firefighting services were started.
Do you know how they'd work?
Firefighters would come up to your house and ask for half of what was inside in order to extinguish the fire, because there's no free market for desperate people.
Ooooor... they'd do the same to your neighbors, because if they wouldn't extinguish your fire, their house could burn down, too.
Ooooor... they'd set stuff on fire so that they'd have who to blackmail.
Ooooor... you could pay them a constant insurance/protection fee so that they'd actually help. And that insurance/protection fee would become widespread, because who wants their house to burn down?
At which point, why not just distribute the cost to everyone since 99.999% of buildings can burn down, and make it a public service?
Which is where we are now.
Anarcho-capitalists and libertarians are basically people who don't know history and would want to speedrun it with great pain and suffering for everyone, along the way.