Phil gave a great quote from the article on passive voice, so I’ll provide a different one:
The treatment of the passive is not an isolated slip. It is typical of Elements. The book’s toxic mix of purism, atavism, and personal eccentricity is not underpinned by a proper grounding in English grammar. It is often so misguided that the authors appear not to notice their own egregious flouting of its own rules. They can’t help it, because they don’t know how to identify what they condemn.
“Put statements in positive form,” they stipulate, in a section that seeks to prevent “not” from being used as “a means of evasion.”
“Write with nouns and verbs, not with adjectives and adverbs,” they insist. (The motivation of this mysterious decree remains unclear to me.)
And then, in the very next sentence, comes a negative passive clause containing three adjectives: “The adjective hasn’t been built that can pull a weak or inaccurate noun out of a tight place.”
That’s actually not just three strikes, it’s four, because in addition to contravening “positive form” and “active voice” and “nouns and verbs,” it has a relative clause (“that can pull”) removed from what it belongs with (the adjective), which violates another edict: “Keep related words together.”
“Keep related words together” is further explained in these terms: “The subject of a sentence and the principal verb should not, as a rule, be separated by a phrase or clause that can be transferred to the beginning.” That is a negative passive, containing an adjective, with the subject separated from the principal verb by a phrase (“as a rule”) that could easily have been transferred to the beginning. Another quadruple violation.
The book’s contempt for its own grammatical dictates seems almost willful, as if the authors were flaunting the fact that the rules don’t apply to them. But I don’t think they are. Given the evidence that they can’t even tell actives from passives, my guess would be that it is sheer ignorance. They know a few terms, like “subject” and “verb” and “phrase,” but they do not control them well enough to monitor and analyze the structure of what they write.
Linguists may very well be incredibly confusing to follow, understand, or read – even to each other. They may introduce new words and terminology when its not necessary. They may speak and write in ways that are both unclear and unhelpful. They often even make grammar signficantly more complicated than it needs to be. Perhaps some don’t know the languages they’re discussing as well as they should, particularly in typological works, but even still.
At least they know what a passive is and that its not necessarily wrong to use it.