Not sure if this chart makes a good case against bike helmets, or just against riding in the US:
- National bicycle fatality rates vary inversely with helmet use.
- Fatality rates vary inversely with bicycle use.
- Bicycle use varies inversely with helmet use.
The cause-effect pointers criss-cross all over all three of those relationships. People don't use helmets where it's safe to ride? Helmet laws or promotion lower bike fatality rates by discouraging bike use, and that reduction in bike useage makes it more dangerous for the remaining cyclists? That's pretty much what happened with Australia's mandatory helmet law.
Of course there are certainly accidents (and risky things you can do on a bike) where a helmet would prevent a severe bump on the noggin. OTOH, there's a "risk compensation" effect where it's been shown that cars drive closer to helmeted riders. The guy on the racing bike in the Lycra super hero costumer and space alien lid knows what he's doing and I don't need to worry about him, while the nut job in the fedora wobbling along on a weird little bike is liable to do most anything and I'd best steer clear.
Part of it is the psychological oddity where drivers, bicyclist and pedestrians have an innate disrespect for each other and wish they could have the road to themselves. I wouldn't be surprised if that effect is magnified in a bike-hostile place like East Tennessee. The bicyclist in the weird clothing is more "other" than the "guy on a bike" in street clothes.