Fallacy:
"If there was a free society without a state, wouldn't warlords take over?"
Response:
This is best answered by Robert P. Murphy's article, serendipitously named But Wouldn't Warlords Take Over?
In a little more detail, (1) with a state they already have, and you're paying tribute and obeying their edicts, and (2) distributed power is a great deterrent.
It must be realized that if there is one band with superior force, yeah, they're going to take over and possibly institute a state. "We must have a state to prevent the institution of a state" doesn't make much sense, however. Maybe "To prevent the institution of a worse state" but it's still just fear-mongering. The hope is that a free society will survive though education and distributed force—there are no prohibitions on building, importing, or trading arms—and be able to repel invasion from without and enslavement from within; but it is certainly possible it could fail… a guerrilla war might be fought to defeat the new tax-eaters; there are many possibilities.