There are no Disney villains.
In this essay, when I say "Disney villain", I mean the archetypical villain from older Disney movies, where the villain is just bad for no reason. Disney villains have no motivation, not even personal gain: they merely are evil for evil's sake.
The idea of a Disney villain is attractive because it's simple. There's no ethical quandary with a Disney villain: while not every villain in older Disney movies actually dies, the stakes are similar: it's kill or be killed. There's no ethical debate about whether it's wrong to kill a Disney villain, because there's no other option. They're the bad guys, and if the good guys pull any punches, the bad guys win. We don't want that, do we?
While Disney villains are fine as a plot device in movies, the problem arises when we begin to treat people as Disney villains in real life. People in real life do bad things, but they aren't Disney villains. There are the occasional mentally ill people who are internally compelled to do things even they believe are bad. But in most cases, people who do bad things do those bad things because they believe what they believe those bad things are good things. Good intentions are easily perverted by fear or ignorance.