If I was travelling and my kid was interviewed this way, first thing I would do is tell the TSO to back off my kid and talk to me...
If they continued to persist, at that point, there would be a REAL situation in progress, as I would be showing my kid how to give a good whooping...
If a kid is showing happiness when talking to someone, then it is fine, but if they are scared, back off and leave them be...
This TSO should be FIRED... after letting me take him into a back alley and beat the crap out of him... let him pick on someone his own SIZE...