I really doubt that unloading the car that way is really going to hurt anything, the winch line is only there to prevent the car from getting away going down the ramp because there is no one behind the wheel to use the brakes. If the weight of the car on that ramp bends the axle there are bigger problems. Now if you are trying to pull it out of a ditch stuck in the mud there are better places to hook up the tow line.
