I don't think I've been condescending to him, but maybe he's picked up on something. I've only ever talked to him about cycling, and it was always friendly, but brief. But that opinion that he is not that bright is universally held. I'm not trying to be mean, that's just how it is. Moreover, when I asked someone who works closely with him if I should bring up this issue, they said "Don't bother, he's nuts."

I simply feel a certain obligation to bring up the safety issues; I might have a perspective that few other people around him could offer, having logged many miles commuting.
I would really feel bad if he got hurt (again), and I had not at least tried to educate him. I just can't figure if there's any percentage in trying, in this case. He hasn't picked up on the helmet and the mirror, why would he listen about not riding 'salmon', or looking instead of listening?