I was writing about the alternative to the government forcing you to be one thing or another which is only tangentially associated with the form of said government.
As for the "never been tried before" issue, you're right. We haven't tried Libertarianism before, per se, but the first few decades of the American government were far closer to the Libertarian ideal (minimal government, maximum individual rights and responsibility) than most will admit. We sort-of have tried that before!
The Constitutional Republic is obviously a superior choice to what we have now, but it is far from the theoretical ideal.
BTW, associating Libertarian government with anarchy is both misguided and rude. Libertarians advocate smaller government, not no government and fewer laws, not lawlessness. There is a significant difference between that and anarchy, thank you very much! ;)