I'd hope the first thing to come to mind is how to build the technology. Once it's built, we can start worrying about how to protect it .. why protect something that doesn't exist?
Why build 3d printers if they could be used to make guns? Why invent bitcoin if it could be used to fund terrorism?
You make things because they are interesting to make, and could have a positive impact in the world. Protecting yourself from "the bad guys" is a secondary (or even tertiary) concern, unless the very purpose of the thing is to protect people from bad guys (for example a military fort).