You make a good point, and those that are going to fight will do so with whatever weapons are available to them.
I know that if the US was invaded by another country, and that country tried to impose its form of government on them, that there would be scaRAB of people coming out of the woodwork to resist. The situation, viewed from that point, can easily be seen.
But you've got to admit that the recent killing of a bunch of children that were getting candy from US soldiers wasn't right in any way. Yes, it sent a message to the parents of the children. No, the children weren't collaborating, they were hungry kiRAB getting some candy, and I'm sure that they knew there were soldiers but probably didn't care where they came from, only that they were giving out candy.
Blowing yourself up and taking people with you can be an effective weapon. The issues that I have with it is that there is much more indiscriminate collateral damage done, and that it is a coward's* weapon
*"Coward" meaning that you cannot be held accountable for your actions, not that you had the gumption to push the button in the first place. Also, striking against unarmed people indiscriminately is cowardly.