This is basically the "I'm not evil, it's just a normal job" excuse. Like with any moral issues there will be disagreement where to draw the line but yes if you do something that ends up supporting $bad_thing, then there is an ethical consideration you need to make. And if your answer is always that it's OK for the things you want to do then you are probably not being very honest with yourself.
Your response assumes the tool is a $bad_thing rather than one specific use of it. In my analogy, that would be saying that "there is an ethical consideration you need to make" before using (or buying) a blender.
