You are just selling BTC to anyone interested. You are not an investigator on the people you sold BTC to. Just like a money exchanger accepting clients without necessarily investigating whether they are going to use it for crimes or not. How would you know?
I forgot to mention that BTC itself is illegal in our country which is the major reason of my fear. I sometimes sold BTC to unknown guy and that's what I'm fearing of. If it was legal, I would have nothing to fear at all.
The news I've read a couple of years go about bangladesh towards bitcoin still frightens me, Imagine they started hunting their own citizen who uses bitcoin, trades bitcoin and any activities that relates to cryptocurrencies. Imagine how hard for that for crypto user in Bangladesh, yet still they trusting the decentralized network of bitcoin for not getting caught, one mistake and you'll be arrested. Thinking of it all, police are going to do as much as the agents needs to do to track a person using alphanumeric address.
And OP, just for a safer transaction avoid making a connection with a lot of people especially in facebook, just a friendly reminder.