Alright, first let's take a step back. Torture is wrong, right? Can we agree on that? Prince Humperdinck was wrong to torture Westley.
As a general rule, it's wrong to intentionally cause someone pain. Perhaps there are some people who think it's "wrong but justifiable in certain cases" (ends justify the means) where you might save lives by torturing someone for information (though the evidence shows that people will say anything to get you to stop torturing them, so it's not usually going to give you useful information). Perhaps there are even some people who would say that it's not always wrong, depending on who you're torturing, because sometimes they're not really people. I'm going to ignore people who would say that for now, because I think there's still an interesting surprise here either way, but let's start from here.
A few months ago I watched the Princess Bride with some friends, and I was really surprised at something that I had never noticed before. I was struck by just how evil the bad guy was - it had never stuck out nearly as much as it did this time when I watched it. He's depraved, heinous, and with a very poor sense of morality, willing to wantonly torture someone in a way that causes the most pain possible. That's why I just couldn't get behind Westley.
Yeah, Westley. Everybody already knows that Prince Humperdinck is bad. As a villian he's so exaggerated that it's not even all that believable. But I will say this for him - though he tortures Westley, he doesn't parade him around. He doesn't rub the torture in his face, or take pleasure in it. In fact, his torture machine seems almost humane (as far as torture machines go) - it causes Westley an immense amount of physical pain, but over a very short period, after which he's dead (or mostly dead). That's almost merciful.
Contrast with Westley. He says... well, I'll let him do the talking.
Westley: To the pain means the first thing you will lose will be your feet below the ankles. Then your hands at the wrists. Next your nose.
Prince Humperdinck: And then my tongue I suppose, I killed you too quickly the last time. A mistake I don't mean to duplicate tonight.
Westley: I wasn't finished. The next thing you will lose will be your left eye followed by your right.
Prince Humperdinck: And then my ears, I understand let's get on with it.
Westley: WRONG. Your ears you keep and I'll tell you why. So that every shriek of every child at seeing your hideousness will be yours to cherish. Every babe that weeps at your approach, every woman who cries out, "Dear God! What is that thing," will echo in your perfect ears. That is what to the pain means. It means I leave you in anguish, wallowing in freakish misery forever.I don't know how many times I watched this scene, yet this was the first time I sat up in my seat and said "Wait, what? How could you possibly be that evil and I never noticed?"
Imagine in your head that this isn't Westley talking to Prince Humperdinck. Imagine instead that it's, say, a member of the Taliban talking to an American soldier. Would you say that would qualify them as a terrorist? As a war criminal, if they actually did those things? Now do you see how evil it is?
Westley doesn't just want to hurt the Prince. He wants to maim him and leave him incapable of taking care of himself, blind him, cut out his tongue so he can't talk, and cause serious pain in the process. But he's not done! He also wants to then torment him with the screams of the people who see him. Rather than just kill him, he wants him to be in emotional and physical anguish for as long as he lives.
Um, that whole desiring someone else's pain? Wanting them to be in physical and emotional pain for all time? That's called being evil.
Here's the thing: I never noticed that in the movie until a few months ago. I had probably watched it at least 10 times before, and not one of them was I ever offended by Westley's wanton cruelty. In fact, I probably cheered him on. How is that possible?
It's possible because Westley is "us" - we identify with him - and Prince Humperdinck is "them." Which means he's less than human. He's not really a person. He's just an animal, a monster, a thing to be destroyed or treated as we wish.
For a long time, people didn't think that slavery was wrong. At least in the U.S. over the past few centuries, it wasn't that the slaveowners were horrible people or enjoyed cruelty, or anything like that. They just made the mistake of thinking that a certain group of people wasn't, well, people. They were convinced that African-Americans were less than whole people - 3/5 of one, apparently. And since they were less, you could treat them however you wanted.
Then one day, people noticed. And now, anyone who thinks slavery is a good idea probably is cruel or an evil person. This is how moral progress is made. At one point, thinking that women weren't as good as men or that homosexuals were evil probably didn't say much about your character in general - you didn't have to be evil to think that.
They weren't horrible people. They just didn't notice these moral atrocities going on right in front of them.
The human default is to go along with what your societal group has told you to do. African Americans aren't people? Okay, then it's not wrong for me to discipline them when they don't follow directions, just like I do with my dog. Women aren't equal to men? Okay, they shouldn't get to vote or hold office or get paid the same for the jobs men do. Gays are evil sinners? Okay, they shouldn't be allowed to marry and if they show any affection in public then we can beat them. Prince Humpderdinck is unpleasant and selfish and sent Westley off to be killed so he could marry this girl? Okay, cut off his tongue and feet and hands and poke out his eyes, and leave him in the street to hear people scream at his ugliness.
It takes an exceptional effort to see the moral mistakes our society is currently making. Moral blindness is the default behavior, and getting past that requires more than just listening carefully to those around you - because they're just as blind as you.
It makes you wonder - in 50 or 100 or 1,000 years when people look back on our society, what are the moral atrocities they'll notice that we have no idea about right now?