There is a thin line. There always will be a thin line, because people will always cross it. Do they do it because they don't see it? Maybe. I'd like to think that some people are misguided, but I can't help but think some people are just power hungry.
I would be lying if I said I don't want power, but I don't want power just for the sake of having power (that, by definition, is evil; if you don't belive me, go play Devil May Cry 3 again), but for the people who can't or won't defend themselves.
Is murder an option? Yes. Always. When you have that much power, you have to have that option. Would I use it? That's a much harder question. Generally speaking, no, I wouldn't. That's not my right. I don't know all the facts, I don't know what forced a person to what. But...if a person can and will do nothing but cause harm to society, then yes, lethal force would be viable. I wouldn't like it, and it would leave a sickly taste in my mouth, but I would do it. There are some people who just cannot be redeemed.
That's not to say any murderer, thug, or rapist would be subject to my wrath, just people who cannot or will not be redeemed.
Could I walk that line? I don't know. But I would sure as hell try.
Apologies if I seem overly optimistic. Really, it's because I am.