What does down hill long boarding have to do with low speed cycling? A bike 15-20mph is much closer to a runner (5-10mph), than your sport (50+ mph). You gonna stop people from running without a helmet?

Their underlying point is we don't have a major problem with people falling off their bikes randomly, we have a problem with multi ton vehicles slamming into bikes and pedestrians. Did you know most bike helmets (not motorcycle ones) aren't tested for the force of car/truck hitting a bike? We need to stop pretending that if people put a helmet on their safe and we can go back to our lives. We need safer separate infrastructure, and if we had that you'd probably not worry so much about helmets.