I go up behind them and flash them.
Those that don't respond don't even notice me. They are the real problem, and they need to have licences revoked.
Its because when I go past them I have a look at them. And they are always in some sort of trance/stare directly ahead and usually pushed up close to the steering wheel.
Their awareness is limited to what is immediately in front of them in their lane.
In my opinion they should not be on a motorway, hell they shouldn't even be driving at all.