Certainly it's regrettable and I'm not trying to downplay suffering and all of that. But simply that under those two assumptions, it's no more horrific to me then having bombs fall on my house, being caught in the crossfire of a shoot out, etc.
Unless there was specific intent to cause undue pain and suffering to non-combantants, it's not that sinister to me.
Oh great, so now a chemical weapon is only bad if you "intend to cause undue pain and suffering with it".
The US army used WP and napalm in Iraq, and they've been denying it since the war started. Now that they admit it, its not a big deal? Bullshit, they used this stuff as a weapon, and whether WP is specifically banned or not its still wrong.
Personally, on the list of ways to die I would pick a bullet to the brain or a conventional bomb taking out my house any day over white phosphorous melting my flesh off my bones.