Now we have people like Martin McGuinness, a former IRA leader, as active politicians in Northern Ireland.
If you delibrately disturb harmony, or deny someone their rights, or take away something by force that isn't yours, you need to be stopped. Because one thing would lead to another and life as everyone knows it would become a living hell.
Step back and look at oppressive regimes over the course of history. They all have traces of evil in them. It's that simple. I admit that good for one might be evil for another, but there's a basic set of things, I guess, the majority can agree on about what's good and what's not.
Suppose a trolley is barelling down a track towards five tied-down people. If it continues, it'll kill them. But, you have access to a lever which would send the trolley down a side-track instead. But the side-track also has one person tied to it. By pulling the lever, you are effectively murdering that helpless, innocent person -- but you would save the other five. If you don't touch the lever, then you are just an innocent bystander who happened to see a quintuple homicide.
In this case, if you insist that murder is evil, and you refuse to be evil, then you have no choice but to let the five people die. But if you allow that murder is sometimes okay -- which is a utilitarian perspective, in the sense that you care more about the ends than the means -- then it becomes much fuzzier whether murder is inherently evil. Indeed, as soon as you give an explicit definition for evil, it becomes very difficult to defend it. The fact of the matter is, the good/evil dichotomy is false and artificial.
Especially if those concepts are touted as being all-encompassing, holding without exception or being superior to other concepts.
Is that evil? Or is that justified?
Some radio hosts promote this: I remember in the last election some host (I don't remember which one) was very clearly promoting Mitt Romney as the new king. (Not to say that this is shared by all of the right-wing, it certainly is not- the right-wing would say that the left-wing doesn't want kings, but dictators).
Also, I think this explains a lot of populist animosity towards Obama: How can our king not be one of us?
Anyway Star Wars (and many other fantasy) is all about this kind of mythology.
There's also, like you say, people who do things we perceive as "bad", but it often comes down to misunderstandings of motives, imbalances of power and so on. If somebody steals bread to eat, it's not a good thing, but I can't condemn the act either. As somebody who likes to think they're a force for good, I should probably see what I can do to improve their situation so they don't have to steal in the future.
But of course this doesn't apply to terrorists or most criminals. The occasional serial killer fits the bill and not much more.
What really gets me is that if you start taking about terrorists like this, saying you should understand what makes them tick, that they think they're doing the right thing, etc., people freak out. I just think we should understand them better so we know how to stop them, but any attempt at understanding is taken as justification for what they do.
You can't characterize all human motivations along this line of rationale. Psychopathy is real. Even recent history is littered with sadistic madmen.
you don't think anyone is evil?
from charles manson to josef mengele, from the killing fields of the khmer rouge to the zetas in mexico - if you have no problem, no qualms, when you're taking an unarmed human being, shoving them in a barrel then lighting them on fire - you should qualify as evil.
some people cause harm for fun. they enjoy it, take pleasure from it. if you don't label them as evil, then you belittle all the people that put themselves in harms way to help others.
Why do criminals and terrorists act like they do? If you ask people they will tell you because they're evil. But actually nobody is evil, everybody wants something positive. The question is just for whom they think it will be positive and why they think it is positive to do. When you think that they're evil on the other hand you don't have to think about anything and just fight them, because good needs to fight evil.