You may be partially correct, but there are road rules stating that the car in the right lane of a multi lane road with a speed limit of greater than 80KPH must keep left unless overtaking. That is irrespective of whether the car in the right lane is doing what they think is the speed limit. If they are not overtaking, including keeping pace with a car in the other lane, they should move left.
It is not the role or responsibility of one motorist to police the behaviour of other motorists, including the other motorist speeding.

