I'm not sure what a radical helmet denier is but I'm familiar with the school of thought that the onus of car safety ought to be borne in part by those who operate cars, and not solely by pedestrians and cyclists.
The example of the Netherlands illustrates what occurs when society actually takes the issue of safety seriously rather than treating it solely as a matter of personal responsibility. (Also relevant to climate.)
Anyway, for your entertainment:
https://www.bmj.com/content/363/bmj.k5094