I'd argue that working on the right projects reduces the likelihood of collateral damage.

Take for example the R9X [0]. Instead of an explosive warhead it has a set of blades on the tip. The US has used it to assassinate single people in the passenger seat of a car while leaving the driver untouched. I'd rather this than dropping bombs on terrorists that come with a blast radius that takes out everyone else nearby.

This seems net-good to me. There are certainly people alive today because of the R9X team's work.