From my reading of this thread and others, I think most of us agree that Mr. Horn, regardless of whether or not his actions were legal, clearly expressed his intent to kill these guys long before there was any chance that he could have feared for his life, and that is a problem. On the other hand, most have had no problem with the idea that a couple of guys who willfully broke the law are no longer available for that kind of work.
I'd suspect that this is a disconnect that most of us have and that we are continually struggling with, whether we admit it or not. And since the threshold regarding when it is no longer acceptable to simply be a good witness is different for each of us, different scenarios are going to illicit different responses, even from the same people. I think this just shows how hard some of these issues are to deal with for many of us, and also that most of us are actively thinking about such things. The more we think, the more we learn, and be better we'll be able to handle situations that might arise.
Hopefully this will be academic for everyone reading this, and none of us will have to worry about anything worse than being "made" at Thanksgiving dinner. But I suspect the things we think about when reading these discussions are going to be of real benefit to at least a few of us over the course of our lives.
So let the debate rage on! So long as we are learning as we go, and not just reacting in a knee-jerk way, then it is worth the time it takes to read and respond. At least that's what I think...