There are irrational people on every side of every issue. Most people are sane and hold their positions for reasons. My $.02 is that helmets do afford some protection, and I do wear one 95% of the time I'm on a bike. I do not think a helmet is an invicibility shield.
So, while I say that, I was hit by a car a couple of days ago. I was wearing a helmet. No part of my helmet or head contacted either the vehicle or the ground. So while I was wearing one, I don't think it made a lick of difference in this particular case. I think that's what I hear most from the lid-less folks: helmets do not protect you from the most serious situations...collisions. I happen to believe they are a great help for the most common, falling from the height of the riding position to the ground. Same thing with MC helmets, they are designed to protect you from a fall height of about 5 - 6 ft tops. About the only thing that protects you in high speed impacts are God (if you so believe) or random chance (if God isn't your deal.)