It's simply amazing how some people just don't get it. Arguments, stats, money... whatever! Just wear a damn helmet and be done with it.
If they work, then so much the better. If they don't, what do you have to lose except the cost of a helmet? Are your really that poor that you can't afford a helmet?
The old saying is true: IT'S BETTER TO ERR ON THE SAFE SIDE!
Don't be stupid!