The Instructor is a volunteer that is teaching so that a beginner has a fighting chance to keep his plane in a flying condition while learning to fly. If we start making Instructors resposible for the loss of the aircraft then we will not have anyone willing to teach. Then beginners are left on their own and I believe we all know the most common outcome of that.

There are some people that will never become proficient at RC flying and will occasionally crash their aircraft. One cannot hold an Instructor resposible for a students inherent lack of situational awareness or hand eye coordination. There comes a point where you just have to let go.