Suppose your neighbor asserts that he is to get 25 percent of your income and brandishes a gun to show that he means business. Or, suppose he says you are not to employ people for less than a certain wage, or that you can hire only plumbers on his own special list of plumbers. We'd consider such a neighbor to be criminal in initiating such coercions. Libertarians and classical liberals say it's coercion when done by government, too.
Yes, government is a special sort of player in society; its coercions differ than those of criminals. Its coercions are overt, institutionalized, openly rationalized, even supported by a large portion of the public. They are called intervention or restriction or regulation or taxation, rather than extortion, assault, theft, or trespass. But, say libertarians, they are still initiations of coercion.
That is important, because recognizing it helps to sustain a presumption against government coercions, a presumption of liberty. Libertarians think that many extant interventions do not, in fact, meet the burden of proof for overcoming the presumption. Many interventions should be rolled back, repealed, abolished.