I certainly think about it. You can’t control what other people do with your ideas, and since I work on noise from aircraft, I am sure that some of my work could be used for stealth technology designed to kill people.
There will always be people who will misuse technologies for one reason or another. I work mainly on engines, and it would be impossible to prevent them being used for military purposes, for example. I wouldn’t work on things specifically designed to kill people, but it’s difficult with things that have lots of other uses.