Clearly some gliders are worse than others, and yes, better if in the hands of a good pilot. But even a moment's distraction can cause the good pilot to find himself/herself in a diverging and irrecoverable situation (kiting).. Whilst my suggestion to ground those gliders was slightly tongue in cheek, would that be preferable to continuing to see tug pilots "grounded" in a literal sense, with the miscreant sailing on unharmed?
The sustained force, mainly horizontal, from the rope really slows down the tug. 2-3 seconds of 700 lb force leaves the tug slow with a less effective elevator, and,as Chris Rollings noted, an elevator which may be stalled.
Sensor measuring sustained deceleration (not just a brief jerk/impulse) is maybe the measure best used to automatically jettison the rope at the tug end?