I didn't say it didn't show any evidence just that its focus was very narrow and didn't look at the wider picture; BIG difference.
From;
http://www.hsrc.unc.edu/pdf/2000/bc_rpt.pdf
A number of studies indicate that properly worn bicycle helmets are highly effective
in preventing, or reducing the seriousness of, head injury. For example, in a study
of bicyclists seen in Seattle area emergency departments, Thompson et al. (1996)
found that any head injury, and serious head injury, were substantially less common
among bicyclists who had been wearing a helmet. A British study (Maimaris et al.,
1994) found a highly similar protective effect for helmet wearers. A study of
Australian bicyclists seen in Melbourne area hospitals also reported that helmet
wearers were substantially less likely to experience either head or facial injury
(McDermott et al., 1994). In an overview of studies that have examined helmet
effectiveness, Rivara et al. (1998) report that helmets reduce the risk of head or
brain injury by at least 70 percent and injury to the upper or mid-face by 65%.
How about a medical view;
http://pediatrics.aappublications.org/content/110/5/e60.full
Bicycling is a popular pastime and mode of transportation for children. Bicycle-related injuries, however, are common. For example, the annual mortality rate for bicycle-related injuries in children in Canada (1990–1992) was 6 per 100 000 children, with a concomitant annual hospitalization rate of 51 per 100 000.1 From 1994–1997, almost 10 000 Canadian children were hospitalized because of bicycle-related injuries. Of these admissions, 35% were because of injuries to the head.
Bicycle helmets have been shown to be effective in preventing head, brain, and facial injuries to cyclists.2,3 Although some authors have argued against the efficacy of helmets,4,5 published systematic reviews6,7 and a meta-analysis8 demonstrated that helmets protect children from head injuries. The Cochrane Collaboration systematic review reported that helmets reduce the risk of head injury by up to 88% and reduce the risk of facial injury by 65% among child cyclists.
The footnotes give you other references that might be educational