based on just OP it sounded like girl over-heard some off-color but totally innocent and normal teenage boy discussion. coming down as the "big bad lawyer uncle" seemed like an extreme over-reaction.
now that we have more facts i can see how he's definitely concerned but there's still a better way to go about it.
bottom line...and i learned the hard way...don't come to CB for sympathy. you'll get none. people will close their mind to additional facts and run with this for a while. it sucks