Your basically making the argument that murder is inheritantly wrong.
Of course it is.
Murder is wrong by definition. If it wasn't wrong, it wouldn't be murder.
If that is the case then soldier's and people who kill in self-defense are just as guilty as any random serial killer.
Killing in self-defence and in war isn't murder.
You're committing the fallacy of over-narrow definition here, by confusing the particular--murder--with the general--killing.
What you're actually arguing is that a certain type of killing should not be considered murder.
If you seriously believe that, then you have to consider the following question: why shouldn't I be allowed to kill
you, at my own discretion?
You might reply, because you haven't done anything to deserve being killed.
But that's just your opinion. Suppose I disagree? Suppose I think you
have done something to deserve being killed?
Suppose, for example, that I find your position on this subject so dangerous, so poisonous, so potentially devastating to society, that I consider it justifiable to kill you in order to shut you up?
To whom would you appeal, in this case? On what grounds could you object to being killed, and still remain consistent?
If you should be free to kill others at discretion, according to the dictates of your conscience, then why shouldn't I have the same freedom?
The problem with your position is that it's reducible to an absurdity. The same principles that you're using to justify the killing of pedophiles and murderers could be used to justify killing anyone, at any time. You're essentially arguing for the legalization of murder.
But if murder should be legalized, then what have murderers done to deserve being killed? If murderers have committed no crime, then why should you be allowed to punish them?