If he can't trade Bitcoin with those he knows it means he has trust issues, and you brought up strangers, isn't that ridiculous? Someone who don't trust people around him should now trust strangers?
That's not ridiculous, I think. Have you read the context of the OP's story? The fact is, the buyer and seller don't know each other; they were simply recommended. Of course, I have absolutely no advice for such a trading method, regardless of the risks; it's a complete waste of time. But there are specific reasons one should do it, even if there are more practical and efficient ways.
It is not about pointing fingers after the deal with those you know, having Bitcoin should be secret, selling or buying from those you know means you are exposed and history is always right, many powerful men are betrayed by those they knew.
It depends on how you manage it, and how willing you're to let others see your privacy.
If those around you can't kill you, those far away from you, the likes of strangers can't get you too, it is always those closer.
those closest to you and those with the opportunity to do harm aren't necessarily those you know. Once you become a target, you'll be approached either "subtly" or "violently." Again, this isn't about trust.