I also agree with Lister.
I've taken a number of people that I didn't really know....but I almost always knew someone I trusted, who knew them well.
I've only one taken a complete stranger, and then I knew that they had a genuine interest in light aviation.
I'm not saying that I wouldn't take someone who walked over to me on the airfield and asked, but I would be very wary of it. If there was a flight school on the airfield offering trial lessons, I'd have to wonder why they weren't using that? Directing them there, as Lister did, would seem like a very sensible move.
A lot would also depend on your own experience level.....if you were a new PPL, or just low hours, or low currency......taking a complete stranger along for the ride (unexpectedly) might not be the best move.
I think Liser is being quite sensible here. (I also don't think you're being vilified either Lister
)