Yep. It's his choice. Not your place to be a nanny.
But here's some truth...
scars ain't sexy.
(That's Brittany Morrow, the "Road Rash Queen." Her choice of gear before this happened was the same as your friend's... a helmet. Read her story at
http://www.rockthegear.org/ )
Instead of pushing him to get gear, I'd ask this guy just one question:
What
exactly do you think is going to happen to you if you go down?
Let him make his own choices. You've made yours and you have your reasons. Stating those reasons is a better way to persuade than telling people what they should do, IMHO.
If your friend is intelligent enough to be worth hanging out with in the first place, he just might get the hint.
I post a lot about gear and ATGATT. The constant drumbeat is why I choose what I choose... leading the horse to water. If that's encouraged someone else to think more critically about protecting themselves, great. That's the goal.