Considering that loose horses in the pasture generally stand for, what, 15, 18 hours a day, how is making them stand where you want them to stand for a few hours unfair? When I first got my Mustang, he was left tied at all times when I wasn't riding him. He had access to water and a hay bag when tied up for the night but he stayed tied. He fought several times and even ended up down once. All he ended up with was a little rope burn around one leg and a mentality to stay tied calmly, exactly where I want him to, regardless of what I tie him with.
If a horse gets loose, nothing may happen except you have to chase him down. However, what happens if he ends up in the road and gets hit by a car. Then, not only do you have a horse who is either dead or needs to be put down, but you also have to deal with lawsuits from the driver of the car for property damage or injuries caused by them hitting a loose horse. 99.9% of the time, a horse will stop fighting before they do any real damage to themselves. Sure, they can get hurt fighting a tie but I would much rather deal with just an injured horse rather than injured people too.