Quite easy actually. I am taking a morals & ethics course. Looking for discussion on this question because it is all but identical to one we are in the middle of working through.
Question stands, is there a moral & ethical difference between someone who is doing good (under their belief system) by doing harm to you; vs you when you (under your belief system) are the good guy.
Now I'm concerned about what they're teaching you in school. But since you ask, let me try to provide a serious response. I don't know if you'lll agree with me or not.
If a criminal bust into your home at night with the intention of killing you and your family (or worse), are you morally justified to defend yourself with force and kill him first?
A real pacifists would say "no," I guess, even if it leads to harm to himself AND to others who can't defend themselves effectively (kids, elderly, etc.).
But I think any sane person would say, "of course -- obviously it's okay."
A very similar thought process says it was right to use armed force to stop Nazi Germany in WWII.
The use of spies and saboteurs, along with a whole range of other intelligence-gathering and irregular warfare activities, are a normal part of war.
"Question stands, is there a moral & ethical difference between someone who is doing good (under their belief system) by doing harm to you; vs you when you (under your belief system) are the good guy."
I would say that there is an objective standard, yes: you instigates the deadly violence first.
Call this the "rule of tit-for-tat". If I don't hurt you, you don't hurt me. If I don't yell at you, you don't yell at me. If I DO yell at you, then the morally equivalent action is for you to yell back.
So, what is the difference in the two positions?
The difference is who instigated the yelling, or the violence, or the murder, or the war.
WHY is that a difference?
You tell me. Why is it wrong for me to walk up and bash you in the face, or to just up and stick a knife in your guts?
Presumably you think that's wrong, but WHY?
It is perhaps simply definitional: it's wrong to instigate violence because we say so, and this is something on which most people, everywhere, agree.
In that context, what's the difference between the English sending in spies and the Germans doing the same thing? Easy. The Germans started a war of aggressive conquest.
Why? Because they wanted to. Was it to bring some sort of good to the conquered? No, it was to enslave them. They attacked. Therefore, it's ok to attack them back.
There's your answer.
If you feel like it, you might give it a read. I think it touches on a question that's pretty similar to the one you've raised. It's called Non-Judgment Day at Yale.
When Michael Kelley was killed in Iraq I was really stunned -- he can never be replaced.