Liddites: a group of people clinging to an outmoded idea and prepared to smash cycling rather than submit to progress. Your average liddite is a handwringer, generally hasn't ridden a bike in ages apart form one or two deeply terrifying trips out with the kids to try to get them interested. Cycling is scary and dangerous, therefore helmets must be worn (which begs the question not only of the real level of danger, but of the efficacy of helmets in mitigating the risk).
Lidditis is the condition where belief in helmets is ingrained to such an extent that not only is any conflicting evidence rejected as heretical, but any evidence that cycling might not actually be a lethally dangerous extreme sport is ridiculed as absurd. In the terminal stages of lidditis, the liddite will use the example of extreme mountain descents on the Tour de France to explain why a helmet absolutely must be worn when pootling down to the shops on your three-speed Raleigh with the wicker basket. Because if Lance wears one, they must be good! An example of the appeal to authority fallacy, by the way.