You ever finish working on something and then think to yourself, "damn, I just created something incredibly evil"?
Usually, we can't rely on things simply not being invented, so we do the next best thing: invent it, and use the invented thing to learn how to manage the risk that thing introduced.
Here's another one: name the private (not gov contractor) orgs who are currently working on fission/fusion or even radiological weapons. There aren't any. For as disparate as the cultures of China and the US are, both realize the fact that DIY nukes are bad and universally disappear anyone going down that route.
Engineering ethics courses all boil down to "don't lie about stuff", not "think about the potential consequences of what you're building".