another point here.. You mentioned that he would prolly like mtn biking. Well with the way he rides now, I would not want him out there on a trail. Not only would he be a safety hazard to other riders, but I could see his actions reflecting poorly on the sport of mtn biking. We have enough knobs out there going off of the trails, buzzing hikers, horses etc. The last thing we need is someone out there with such reckless disregard for others.
And yeah, I wouldn't ride with him either. There were times when my husband TRIED to go sans helmet on our family cruises and it just was not an option..