I have little faith in the unbiased nature of someone named war4peace. But I'll bite...
The engineer designs/builds the stuff. Someone else uses the stuff unethically.
True an engineer can't know ahead of time exactely how/when/where say an American combat rifle will be used. However, seeing that after 9/11 we invaded 2 countries that had little (Afghanistan) and no (Iraq) connection to it but do have strategic uses/oil (rich tasty oil) its pretty clear the US will use those weapons as it chooses, unilaterally (more or less) and in violation of international law and any sense of morality.
It would be like suggesting chemical weapons research for Bashar al-Assad might be used to find new cures. Technically true but the precedent suggests otherwise.
Pretty much anything can be weaponized; some things more directly than others, but in the end, whatever you design, think, build, imagine can (and likely will) be used to hurt others, be they human beings or animals.
We should build more powerful nukes because people would just knife each other anyway?
Logistics matter a great deal, saying the internet is worthless because USPS is a reliable means of transmitting information would be moronic.
if John Doe is an engineer and he's offered a military industry job, then if he turns it down, someone else will take it.
And someone else can deal with the ethics of that.
"The standard you walk past is the standard you accept." Don't pretend you have higher ethics than what your actions reflect, you don't.
Also, the article implies that an engineer should think of all possible implications when working on something, including ethical use of the product. Which brings back the original statement: you can't make sure that the product will only be used in an ethical manner. It's an impossibility. The only assurance would be that no engineer builds anything anymore. And I'm pretty sure that most people would loathe shivering in a cave with only a raw pelt covering their skin. Just sayin'...
I completely agree that there could be times an engineer is working on a project and not predict how that technology, even fairly directly, could be used for purposes they would never condone. I, personally, would only ask that an engineer make an honest attempt to determine if immoral uses are possible and reasonably likely in lifetime of the technology and use that to judge the work as ethical or not. A standard would need a more concrete definition and thus more consideration than I can put into this comment.