In the rise of Fundamentalism in the early 20th century, the rhetoric was exclusionary. That's the defining feature of Fundamentalism, as much as anything. The rhetoric worked by dint of exclusion, by ruling out other possibilities, so that "Christian" was understood to only mean and necessarily mean one thing and not another.
The arguments were structured particularly so that the other side, the opposition, was not just wrong, or at least never merely wrong but always something more than wrong. "They're wrong, but more than that ... they hate God" and so on. The opposing arguments of modernist or mainline Christians were framed as being in bad faith, for example, as secret Trojan-horse atheism. The Fundamentalist rhetoric worked this way -- rephrasing, re-framing, re-interpreting non-fundamentalism as impossible, as not really Christian, as more than wrong.
That's not to say, however, that's all that was going on with the rhetoric.
For example: look at the other thing that's going on in the Fundamentalist's rhetorical use of the word "weasel."
W.B. Riley, insisting in "The Faith of the Fundamentalist" that the only way a Christian can read the Bible is without any interpretive method, says Christians can have "no sympathy whatever for the weasel method of sucking the meaning out of words and then presenting the empty shell."
William Jennings Bryan, at the really-too-famous Scopes trial, says people who aren't really Christians but try to read the Bible in a way that will undermine the truth of Christianity "attack the truth of the Bible, not openly at first, but by using weasel-words like 'poetical,' 'symbolical' and 'allegorical' to suck the meaning out of the inspired record of man's creation."
The word's notable just since it's not used so much any more. It's a farm boy word. According to Google's ngrams, the use of "weasel" in American printed material peaked around 1900, rose again in the 40s, and has dropped off since then. "Weasel words" skyrockets around 1915 and peaks in the 1940s -- the golden age of Fundamentalism, though I'm guessing Neville Chamberlain also got a few mentions in there.
The point is, this isn't an insult you use in the cities. This isn't a word you use in the suburbs. It's a rural-rooted word, a country insult.
It works, for both Riley and Bryan, by characterizing their opponents as more than wrong. Using hermeneutical methods to read the Bible isn't just misguided or simply in error, it's a trick. It's a sneaky way of making the text meaningless, of sucking the insides out.
This is all pretty standard. What's interesting though in this moment of rhetoric is not particularly how it's an act of delegitimation, but how it's an assertion of masculinity. The opposite of "weasley" is "manly." To weasel, to be weaselly, to use weasel words or methods, is unthinkable for men's men. Inconceivable. Manly men don't mince their words or make them fancy, but simply say it straight -- homophobic implications very much implicit here.
The other thing the use of this word does, besides the exclusion, is construct Fundamentalism as extra, extra manly.
This is the same idea that makes offensiveness a mark of truthfulness. Manly men, in this cowboy conception, don't care if the truth hurts your feelings. It's the truth. It's muscular, not gentle.
This has an exclusionary function as well, of course. Being a liberal, being someone who might want to say that something about the Bible is complicated and not just simple and plain, but needs, perhaps, careful consideration and nuanced parsing, is framed as wimpy. And who wants to be that? Be a man, be a Fundamentalist!
Yet, it's interesting too because it evidences a felt need to assert the manliness of Fundamentalism. It is an act of ginning up manliness. I.e., it's a response born out of a self-perceived lack, not some excess that simply splashes over there's so much of it. It's a self assertion.
This same thing can be found in the style of Billy Sunday and in the stories about the sexual magnetism/woman-attracting charisma of the circuit-riding preachers. This move makes sense, too, in the historical context that "church" was marked in the Victorian-era society as part of the domestic sphere, as women's space, and ministers were understood to be effeminate, and the whole thing -- religion, church, morals, prayer -- was understood to be very not masculine. So the Fundamentalists, are pushing back against that.
Here, though, it's in all the use of the word "weasel," which strikes me as a funny moment of rhetoric.