So our knowledge about guns is bad because guns kill? I can't explain it more, sorry. I think the explanation I've given is very obvious - technology can be used badly, but it's always the people who do it, not the technology itself. Technology is neutral, you can simply not use it - knowing it still might prove important for development of other technologies, e.g. for prevention, reparation, ... after the original technology is used, in case of nuclear weapons for example (how would we know how to prevent and treat radiation illness without knowing anything about nuclear physics), and at the very extreme, the technology itself will do nothing - until people start using it. People are bad, not technology.