I can feel your pain a bit. I grew up with a ridiculously strict mom, and although I wasn't in to biking when I was your age, she said 'no' to lots of other normal things that your average, 18 year old, red-blooded American boy should definitely do.
It looks like you have plenty of good suggestions here, and the trend points to education. If you educate someone on the subject of touring, hopefully they'll start to see things in a new light.
For instance, I still get strange looks from people who see me ride my bike into work. A whole 3.5 miles. I work with people that live closer to work than me, who have flat-out thought I was insane when I suggested maybe they should try biking/walking to work every once in a while. Hopefully I can drop some knowledge on these folks.

Good luck!