Premise: All use of force risks collateral damage
Premise: Self defense requires the use of force
Conclusion: Self defense involves risk of collateral damage

Premise: All use of force risks collateral damage
Premise: Fighting evil requires force
Conclusion: Fighting evil involves risk of collateral damage

Premise: Self defense and fighting evil involve risk of collateral damage
Premise: Some people object to war against Iraq on the basis that collateral damage is morally wrong
Conclusion: These people think that fighting evil and self defense are morally wrong or these people are inconsistent