I avoid doing business with some I know, because you tend to trust them too much and that is a very easy way for them to scam you or sell something that is stolen to you.
So what's your priority option, doing business with random guys? I think this is the opposite of what most people do. Dealing with people you know isn't about trust; you simply have a greater chance of recovering your losses because you can identify them better.
You know the right answer but you choose to pretend like you don't, the right thing to do is trade Bitcoin the way it is suppose to be traded, if you want to buy Bitcoin it is safer to buy from exchanges, centralised or decentralised that's your choice to make.
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?
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.
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.