Just wondering how sidelining a green colt has become a "dangerous" technique?

This has to be coming from a novice that has never worked with horses that have not had human contact. Sidelineing and scotch hobbling and using soft ropes to rub the body and pick up feet has been in practice for over a hundred years and works as well today as back then. Is it not more a DANGER that an inexperianced person be working with a colt let alone a wild or undomesticated one! I think thats green X green =black and blue. Lets hear from some competant horse people.