Appropriate Retaliation

[Downthestretch55]

Sham,
Initially I blew this thread off as it seemed too horrible to contemplate.
Then I went back and reread it. When you said this, you nailed it.

"Is there ever a line that can be crossed by the terrorist that would make it acceptable to kill innocents in order to stop the bad guys."

Your question is quite profound.
I'll just say that it's a matter of "perception". Which side of the fence are you standing on?
From the US position, appropriate actions have been evidenced.
From the Iraqi position, they might see exactly the same and also justify their response.
It's far too easy to see others as "bad guys".
Suffer the innocents.

btw...I agree with you that it will be biological...but not as you have conjectured.