You can't prevent someone from doing something stupid once they've made up their mind to ignore your advice. I would have had to watch his friend's folly also. Maybe from a little more of a safe distance incase he did hit those power lines, but I would have had to watch. And show the video.
I had a similar, albeit less consequencial experience with a fellow who was determined to maiden his new foamy Cessna 182 even after I offered to buddy box him for his first flight on one of my planes. I had my equipment right there and even showed him how it worked with my Super Cub, but he was determined to do it all himself. Of course, his first ever flight lasted about 20 seconds and his plane ended up in three pieces. Now he wants my help.
Maybe Skeletor's friend will learn something and try to be more responsible next time, maybe not. But......, if he hits those power lines next time, it will cost him a lot more than a plane and some pride!