So we can safely conclude that 40% are proper cyclists who nod and 60% are silly weirdos that shouldn't allowed into our group.
I think there should be some sort of campaign, maybe radio or TV, advising cyclists of the correct etiquette. When we get our act together, it would go some way to demonstrating to drivers that we are a civilised bunch and care should be taken around us. I'm thinking something along the lines of...
Be a proper cyclist, be a safe cyclist, nod hello. If you don't, you're only making it more dangerous for the rest of us.