Probably because the articles are talking about how the AI will be used in immoral ways, and that the people who know that and continue doing the work must be morally compromised.

I know that there might be $several ways those highly-paid engineers might still rationalize their work. Some of them might have ideological reasons to treat entire classes of people as unworthy of life. Within the model of their ideologies, the most evil things might be perfectly moral.

I wonder what reasons you have to disagree with people's moral stance against using AI as a weapon.