Thanks for the input guys; I loaned him a bike because he simply needed a way to get around, I will be taking it back this week since I know that he does not care for it/watch it as well as he would his own and I don't want our friendship ruined by something petty like a damaged or stolen bicycle. He'll be done repairing his own bike soon anyway.
I went out on my bike alone tonight, meeting him at a central place rather than riding together, so I wasn't stressed out from daddying him around. I think I'll do this more often, but I hope it doesn't end up with him being hit again from ninja riding alone; the only thing I've taught him that really stuck is taking the lane, which he will do alone in pitch darkness. I'm not buying him any lights, and hopefully he's not waiting for me to do so (I bought a $15 lightset for another friend last week) because he should be thinking about how to prevent another accident from happening rather than riding around like he's in Utopia. Even in Utopia I'd think ninja cyclists would be viewed as asshats.