Again, fallacies would be funny if no one believed them.
Most pro-helmet statistics are too self-interested and are thus suspect—to actually quote Bell rationalizing their own product is absurd. Comparing motorcycle helmet research to bike helmet reality is also absurd. The helmets themselves are too different in construction and weight while the conditions and expectations are different as well. This line of reason should be avoided. Ad hominum attacks are useless as well, blathering idiots can make salient points and geniuses can be wrong. To descend into such attacks basically concedes an argument.
Real scientific research into the effects of helmet effectiveness is problematic because most cycling accidents are not reported and subjecting real humans to accident like trauma to the head is highly unethical. Bike helmets have their uses but mostly, the helmet argument circumvents real safety advocacy by focusing on the easy solution rather than real solutions for cycling/road safety.
On the other hand, pro-helmet advocacy definitely has problems. Two reports I have seen on helmet advocacy show a problem with the methods of advertising helmet use. The first, from Australia, show a decrease in cycling popularity following passage of mandatory helmet laws- attributed not to the wearing of helmets but rather to the portrayal of cycling as dangerous enough to merit a law mandating helmets. The second was a study of risk behavior with and without helmets. The study basically suggested that the mere act of wearing a helmet alleviated riders fears making them subconsciously more bold and thus more of a danger. Again, this increased risk taking could be attributed to the pro-helmet propaganda (stating that helmet mitigate all the danger of cycling) rather than the actual helmets.
I wear a helmet mostly because I have to in order to ride with the local group and while it offers some protection, I would never suggest that it offers substantial protection. A guy fell last week into a ditch, broke his collar bone (4 places), two ribs, and his helmet (very little visible damage). Had he not been overlapped and touched wheels (multiple times) nothing would have been damaged at all—those however, are the risks of a paceline. Luckily, he was the only one to go down. This is not, however, proof of anything but the rules against overlapping wheels in a paceline.