Blogenspiel has a gripe about NPR saying that Harriet Miers was Catholic before she converted to Christianity, as if Catholicism isn't a form of Christianity. One of her commenters chalks it up to "falling into the evangelical rhetoric."
Perhaps the problem is that NPR reporters aren't familiar with Christianity in any form? I've noticed that they tend to mis-state or seriously mis-understand basic doctrines, tend to use the terminology of Christianity in awkward ways that imply a lack of familiarity, and tend to use the word "Christian" as a signal of disapproval.
So, though I didn't hear the story, given that it was on NPR, I suspect the reference to evangelicals as "Christians" was not intended to be a concession to evangelical rhetoric, but was instead a signal to the audience that evangelicals are the "bad guys" (which would put Catholics in the unusual position of being good guys, or at least the lesser evil on NPR).
Of course, they like to use "medieval" as an insult too, so whenever they refer to the Catholic Church as medieval, I always think of Merry's reaction when the Sackville-Bagginses accuse Frodo of being a Brandybuck rather than a Baggins:
"Did you hear that, Merry? That was an insult, if you like," said Frodo as he shut the door on her.
"It was a compliment," said Merry Brandybuck, " and so, of course, not true."