I have a colleague at work who suffers from the selective purblindness that affects many motorists. All cyclists are anarchic, lawless gutter scum, no motorist ever does anything wrong, that sort of thing. The other day she came in huffing and puffing, and said "Those cyclists, they were RACING each other down the road this morning, they were overtaking each other and EVERYTHING. They should make all cyclists have a registration number on their bike so that you can report them to the police." I considered laughing in her face, but when I realised she was serious, I just said "Yes, because that works so well with all the other road users, doesn't it?" It took her a while to get the point.