Within contemporary linguistics (the study of language and the way languages work), there are two approaches to grammar, prescriptivism and descriptivism. A brief understanding of these terms gives context for how usage guides like Strunk and White’s The Elements of Style are aimed at the general public as well as how the language is studied as a formal science.
People who consider themselves wardens of the language are prescriptivists. Firmly convinced there is a ‘right’ way to speak, they believe there is a ‘correct’ English that sets the standard for all other variations of the language. Not surprisingly, this correct English is considered superior to all other forms. Statements such as, “if you want to get a good job, you had better get rid of that accent,” mark a prescriptivist attitude toward language, even if the speaker has good intentions. Prescriptivists tend to be highly unreceptive to change as it applies to language, often making the highly contentious claim that language is constantly eroding and has gotten noticeably worse, even in their lifetime.
If prescriptivists are of the opinion that there is a correct English, then it shouldn’t surprise you that the most outspoken advocates are practitioners of this form, of course. Armed with the belief that their English is fundamentally superior to all others, many prescriptivists communicate in a haughty and sanctimonious way. Strunk and White are clearly a part of the prescriptivist camp, Struck probably more so than White. If you look closely at the writing in Elements, his talk of people being ‘illiterate’ if they use certain terms, or ‘vulgar’ if they use others (always ones that don’t suit his liking, incidentally) suggests that he feels himself above the great majority of his readers.
By contrast, descriptivists are curious about how languages evolve as living organisms and about how languages are actually used by people (rather than how rules dictate how they should be used). They reject entirely the notion that languages stay static, as well as the claim that certain forms of language are inherently superior to others. Most linguists, Pullum (the linguist from the last post who was so critical of Strunk and White) very much included, are descriptivists. In short, their intention is to describe language, its features, and most important, its adaptations over time. Critics feel descriptivists take a no rules approach to grammar. This is hardly true, and Pullum acknowledges that English has plenty of rules that brook no exception. Descriptivism simply chooses to advance the belief that there are times when many valid forms exist within the language rather than one right way.
If nothing else, a brief knowledge of these two approaches should make you slightly more skeptical of dogmatic pronouncements about language, as such statements can sometimes be ignorant of the highly much more complex aspects of the grammar.