I think the correct term to use in this case, is
"When engineers start acting religiously..."
As a person doesn't need a religion, to act religious; I can be religious about canned goods or martial arts, or perhaps, engineering.
I do agree that using the term "religious people", while the meaning is understood, makes a generalised assumption about a larger group of people who do not all adhere to the imagined stereotype, and it casts them in a negative light.
I suppose that the point you're making is that zer0gravity used the term "religious people", and that seems to be acceptable to most people, few object to it;
whereas "people of color" or any other term that is deemed unacceptable to make that kind of negative assumption about, would not be okay.
And that's a rather big double-standard.
Regardless though, the meaning that zer0gravity was trying to convey, was clear and understood.
I think taking up offence at zer0gravity's comment and use of the term "religious people" just detracts from the topic being discussed;
and I highly doubt any ground will be crossed on the point you're trying to make; at least on this page and topic.
True, though this story sounded more like one engineer convinced of his godhood and a bunch of clueless managers who ensure that the only way you can keep your job is to believe in the greatness of the solution and its author...