Using your line of language all extortion fees are paid voluntarily, correct? So is intercourse under threat of having your throat cut, right?

"Voluntary" normally (when not explicitly pointing out the specifics) means different things depending on context, as it then should. The common theme with anti-capitalists is that they confuse the proper uses in these contexts - such as the difference between discussing free will and it's narrow practical defence in the legal realm - and that they strawman the anarcho-capitalist position as being one for a society where no positive moral or contractual considerations are given to the poor, the weak or the person currently residing on someone else's property.