IMO a controller calmly telling a pilot to ignore all the big red "don't ever cross this line under any circumstances ever ever" lights deserves the contempt it was apparently given
Just occasionally a technical problem will prevent the controller from changing the stop bar to green or out. Used LHR a lot, sometimes heard or said myself, (callsign)"we have a red bar coming up" if our clearance was to a point beyond it. No big drama or cause for agitation really.