Earlier quoted context omitted.
What you call anarchism is really a very specific subcategory called anarcho-capitalism. In any case, it is similarly naive as other strands of anarchism. Power vacuums will inevitably be filled. The question is: What do you want them to be filled with.
Calling something naive doesn't make it so. Saying "Power vacuums will inevitably be filled" doesn't make it true because you say so. What if there is no power vacuums and people don't want to be ruled by anyone? Is there anything to be filled then? What I personally consider to be naive is the idea that governance is inevitable, but that's no logical argument against government, so I don't go around saying it.
Society needs a response against this minority, and this response needs to be organized somehow. Somebody will be in a role of organizing the defense of society against those who would seek to rule over it. But now it sounds as if that somebody (or somebodies) are in a pretty powerful position, no?
This is why so many anarchists are so counter-productive. Of course the basic notions of allowing personal liberty and to be baseline-skeptical against authority are good. The thing is, you won't actually achieve personal liberty by just getting rid of any sort of government-like thing. It would be more productive to discuss what kind of government is best suited to protect personal personal liberty.
Note that none of this is a defense of governments as they exist today. It is more a reminder that those who most seek to overthrow what they perceive to be the current oppressors are the most likely to end up being the future oppressors. Or, in comic form: http://www.smbc-comics.com/?id=3246#comic