"WIll all those saying it was fine please also answer the question where do you draw the line and how?"
It's been answered before on this thread, but for those not reading much of it, the dividing line is between controlling and simply speaking a line that his father fed him. Did the kid check intersecting taxiways, estimate the time-to-touchdown of the aircraft on half-mile final, ensure clearance from the previous departure and then tell JetBlue to go? No. He spoke the words his daddy told him to speak, and he may not even have known what they meant.
His sole responsibility was to enunciate clearly (and if he hadn't, "Say again?" would have worked just fine). Any responsibility beyond that crosses the line you wish drawn.