He is quoting Murray Rothbard in For a New Liberty. The full quote is:

"For centuries, the State (or more strictly, individuals acting in their roles as 'members of the government') has cloaked its criminal activity in highsounding rhetoric. For centuries the State has committed mass murder and called it 'war'; then ennobled the mass slaughter that 'war' involves. For centuries the State has enslaved people into its armed battalions and called it 'conscription' in the 'national service.' For centuries the State has robbed people at bayonet point and called it 'taxation.' In fact, if you wish to know how libertarians regard the State and any of its acts, simply think of the State as a criminal band, and all of the libertarian attitudes will logically fall into place."