The libertarian would be carrying a concealed weapon, likely modified to be fully automatic. The anarchist would be carrying a single Molotov cocktail and a can of spray paint.
The anarchist has one, and only one, chance to take out the libertarian, and that is with a direct hit from the Molotov. Even then, the anarchist would have to throw it before the libertarian can draw his/her weapon. After that, the libertarian would make mince meat of the anarchist.
The anarchist does have a chance of avoiding the fight altogether by spray painting "Good Government = No Government" on a wall, after which the two foes would pause and realize that they have basically the same views.