If they gave it a moment's thought they'd realise that in group situations, it's often easier to overtake cyclists 2 or more abreast, as there's less linear room to navigate.
To be honest, that diagrams fails for me.. even as a cyclist.
How often do drivers really come across a group of nine riders and if they did then any fool amongst them would appreciate the group bunching up.
I think 2 or 4 riders are the "groups" that cause frustration. In this situation I struggle to paint a picture (like the above) that can show a benefit to a driver and i think it better to just share the road and single out when a car is around to save holding up traffic, even if that means slowing and moving over too, why not...it'll hold me up a lot less than I could hold them up by being obstinate and riding by the law, if not by common courtesy.
I think the problem is one of sharing...introduce one stubborn rider to one stubborn driver and pretty soon you have yourself a radio phone in, followed by a reciprical internet chat that attracts all manner of ignorance and conflict...where there needn't be any.
so, to me the joy of riding two a breast should be treated as a privilege...unless of course I am riding in a peloton of 9 riders.
In busy towns I find it possible to ride two abreast in some instances but these are mostly limited to bus lanes and CS paths.
I shall duck for cover now.