In the end, being moderate libertarian is like being a little pregnant. Something is either moral or immoral. If you think the idea of gov is morally okay, then how do you draw the line between gov and non-gov? And why the government cannot be absolute? Why democratic majority cannot kill minority? Why certain actions on part of some people are evil (theft, threat of murder), but on part of others are moral (taxation, arrests)?
For me at least, the difference is pragmatism. I'm open to the idea of anarchy but I'm open to nuclear experimentation too. Makes sense in theory, could be great, but let's test it somewhere that isn't my home.
Would you try to answer questions about morality of the government? Why some human beings can take by force while others cannot?
Regarding testing: you are living in anarchy already. Each time you negotiate with people, each time you protect/insure yourself peacefully without threatening anyone or being threatened directly, then you enjoy natural anarchy. I bet you don't vote with your friends where you go drinking and then force minority to obey? Government intervention takes very small part of your personal and professional life, the rest is total anarchy based on mutual respect and negotiation. Now my question is: why do you give a special role to government and what do you fear if it goes away?