My thought afterwards is some people are naturally drawn to athletic activities, some just aren't..and there may be a good reason why that's so. You can push, you can encourage, you can try to protect them, but the day is going to come when you just are left thinking... really, what the eff was that all about? And, then you feel quilty for the carnage they do to themselves.
I think you have presented a very clear analysis of the situation. This individual's heart just truly was not into cycling that much. I understand that a broken hip is fairly serious, but if he had a deep-seated love of cycling like many on the 50+ sub-forum, he would be already planning his return to the bike.
Also, there is nothing for you to feel guilty about. He ran into you, after all. It sounds like this individual's fitness needs would be best met by "water-walking" in the pool at his neighborhood Y.