I believe you are referencing this answer
The question you have to answer for YOURSELF (not your company) is will you be able to sleep well if one of these guys gets fried? Since the customer has disclosed his unsafe intention, I think that you should not feel obligated to provide the part. Yes, he may just go elsewhere to get the part, but that is on him.
And to be honest, that's not the greatest answer I've ever seen for a situation like this. It is a lot bigger of a question than being able to sleep at night, because Professional Engineers are held to a higher standard than the "Can you sleep at night?" test.
If we look at the National Society of Professional Engineers Code of Ethics, specifically
Section II, Rules of Practice, we see:
- Engineers shall hold paramount the safety, health, and welfare of the public.
- If engineers' judgment is overruled under circumstances that endanger life or property, they shall notify their employer or client and such other authority as may be appropriate.
And it's very clear that there is a stated obligation upon the part of the PE to contact the client in cases where life or property is endangered.
Ultimately, I think your question is addressed more by this:
Are engineering ethics objective or subjective?
And the answer there is "both."
Objective guidelines are laid out (as referenced in the NSPE code), but the applicability of the guidelines to any particular circumstance may be a somewhat subjective affair. Some questions are clear-cut and without ambiguity. Others rely upon the context of the situation and the Engineer's experience in order to be properly assessed.
It's good that you pointed out Good Subjective, Bad Subjective blog posting as it calls out several points under the section "Guidelines for Great Subjective Questions" that go a long way towards identifying subjective questions that are still answerable within the SE Q&A format.