You'd added a lot to this discussion and moved it forward.I thought of perhaps a better scenario for Harris' point. It goes like this:
Some guy comes into your house, with a gun, and tells you his is going to shoot your children. He hasn't done it yet and you don't know whether he has killed someone, but you have a gun that he cannot see. Is it acceptable for you to kill him for that proposition?
That's the clearest case that I can come up with supporting Harris' argument. It's kind of an interesting argument to say "When the US bombs terrorist planners, they are killing people for their propositions" but it totally misses the point that such planners have, in the past, fomented the mass death of innocents. So there's more than a simple proposition to kill, and a belief system enabling that killing, and he's sort of skipping over that.
I think he needs to add in the axiom "past behavior is the best predictor of future behavior" to better support his argument.
It's too bad you can't be here...always....<sniffle >
I would like to point to the importance of belief structures. Al Qaeda is more than a collection of beliefs, it's a system of installing a specific belief structure, that reliably produces people who act predictably. In that way it is different than the religion that provides the core concepts.
I would also like to point out the difference between the principles that Harris is talking about and the possible applications of it. The practical applications of this principle are highly problematic for a myriad of reasons. It's so messy. We need to acknowledge how far from ideal our responses to threats are.