Do you also lecture people who smoke, over eat, do drugs, drink to excess, engage in unsafe sex, drive over the speed limit, don't get their shots, refuse to go to the dentist, don't exercise, etc.?
I have a great deal of respect for the cyclists I was riding with. They are not stupid or irrespsonsible people. They have incredible bike handling skills. They have evaluated the risks and decided that they don't always need helmets. It has nothing to do with being "cool" either for these people.
Making a judgement about someone you don't know is not very respectful. It's like junior high school. They're not wearing the "uniform" so they're not real cyclists.
Whatever.
V.