That's ridiculous. Don't know who he is, and I won't be reading his murderous nonsense. It sounds like some neoconservative who wants to kill children in foreign lands because "they are all terrorists anyway". And it also sounds like those cops who view all citizens as dangerous criminals.
I don't even agree with him and I don't think its comparable.
Foreign wars necessarily require murdering innocent civilians (those who have committed no NAP violation) and theft (via taxation) to fund the wars. Cops who view civilians as dangerous criminals are wrong because the vast majority of civilians, and even the vast majority of civilians who break the law, are not in fact dangerous and are not in fact NAP violators. By contrast, all cops are REQUIRED, as part of their jobs, to violate the NAP. And its really impossible to use proportionate force to protect yourself from the State. With the amount of resources the State has, you could even potentially (I wouldn't do it, and I wouldn't advise you to do it, and I wouldn't advise you to advise anyone else to do it) even argue that being pulled over at a traffic stop is an encounter that justifies deadly force. A couple minutes of your time and a couple hundred bucks isn't worth that to me, and I doubt it would be worth it to Cantwell either, nor to pretty much anyone else who would be contemplating it. But the bottom line, the unfortunate reality, is that the only way to stop that theft is to kill the assailant. Again, personally, I'd settle for calling the guy out on his theft and then allowing him to do it, but that's just me. From an NAP perspective it seems to me that it would be justified to end that encounter by any means necessary. It isn't comparable to the child who steals a piece of candy from the store, because the cop has the might of the (physically) most powerful worldy instituion, namely, the United States Government, backing up his cases of murder. Move forward to an actual attempt to kidnap (arrest) someone for a victimless crime, and it seems pretty clear-cut to me (again, from a legalistic, NAP perspective). And the fact of the matter is, a cop gets himself into that position (putting himself in a position where someone could justifiably use deadly force against him [again, from a legalistic NAP perspective, I'm not saying it would be right, and I certainly don't suggest it]) on a daily basis.
Here's where I disagree with Cantwell. I disagree that the death of cops is something to celebrate. The loss of ANY human life is something to be mourned. Even if taking the life is something that you really did need to do, even if it was completely justified (and I'm not saying that's the case here, I'll address that in a minute) its still sad. You left a family in mourning, and its very possible that the person you killed died and went to Hell (I know Cantwell is an atheist so he wouldn't care about this bit). That's a serious thing, and not something to take lightly, even if it did need to be done (I'd kill a cop who tried to kill me, but I wouldn't celebrate his death ,and I'd be saddened that I had to do what I did.)
Here's the other point on which I disagree with him. While I do believe I would have the right to use deadly force to protect myself from being robbed or unjustly arrested/kidnapped (Do I need to provide the above disclaimer again? Just in case, I'm talking about rights, not suggestions, I don't suggest that you exercise this right in this case) and I'd have the right to help someone else to do so if he requested my help, I do not think I have the right to kill on behalf of someone who would not want me to. For instance, say you (B4L) are pulled over at a traffic ticket. You decide to comply, whether because you don't actually see the injustice of what is happening, or because you would rather not end the life of the robber in blue. The next day, I go to that cop's house and shoot him on the grounds that he has stolen from B4L and will do so to other people in the future. This, to me, is completely unjustified. Its not even really close, for me anyway. I would say I committed murder, in that case. Cantwell would say I was executing vigilante justice, but I don't really think so. It wasn't my place to take the action, and nobody even asked me to take it on their behalf. I just saw somebody who I wanted to kill and I killed him. I don't think that's justified.
Mind you, I was talking about justifiability (in an NAP sense) not what I personally would do or would justify. Personally it would take quite a bit more than that before I'd consider lethal force.