I do think intent can matter at times. Perhaps what I'm more zeroing in on is that idea that I don't find saying you didn't mean to, when you repeatedly kill civilians in very large numbers, such that certain countries have a long history of being on the receiving end of American collateral damage, as an acceptable rational/excuse. (This last part is why I think you're examples are not particularly apt)
Your intent just stops mattering as much when the body count gets to a certain number and you show no signs of changing the behavior.
How about if a junta relies on that a democracy don't want to pay those prices and creates a situation where blood will flow if they don't get their will?
Arguably, both Japan 1945 and Saddam Hussein are cases of that.
Do you REALLY want dictators to rely on using their own people's suffering to get out of e.g. sanctions or surrender? I doubt it...
Sorry for coming in late. I bother writing these answers because I used to have similar opinions as you before my hair started to fall out. You are a standin for a young berntb, I guess.
You're wrong.
If an airliner (or even a weapon) goes astray and kills my family, I am going to be angry, no doubt about it.
If you've deliberately targeted my family, my anger is going to be greater by several orders of magnitude.
For example, this case that was in the news today:
http://www.startribune.com/lifestyle/156366185.html
Suppose the phosphorous did get there through some type of negligence on one of the nearby bases (seems plausible, at least).
Are the woman and her family going to be angry? You bet. Are they going to file a monster lawsuit? Almost certainly. Are they going to declare war on the United States, or (try to) kill a few Marines? Not a chance in hell.
Intent matters.