This is a really interesting post, Sam. Funnily enough, I recently have been exploring anarcho-capitalism, and trying to figure out what I make of it.
The concept appeals to me in many ways. Also, I think its proponents do believe in the goodness of humankind.
However, I don't know if any philosophy can stand up under all circumstances.
It's difficult to assess hypothetical situations. But, just as an example, I've wondered how thoroughly an anarcho-capitalist could have stuck to his or her views in Germany, just before the Second World War.
I agree and have that disagreement with many of my anarcho friends. If you took away all government today, I dont think people would be ready for it, and new forms of government would rise out of people's fear. That's why I believe in a more gradual transition. An anarcho-capitalist would probably not have fared well in Nazi Germany since they were for more intervention in people's lives and more control over indust, much closer to today's left than right in general.