There is a rant that I used to share with any willing audience when I was an undergraduate student in Calgary, inspired by my burgeoning knowledge of how language works, and how different that is from the opinions spouted by language mavens.
I learned, through the brave confidence of a few close friends, that it was becoming a bit tedious to hear this rant over and over again – despite the inherent and unquestionable validity of its content, of course.
So I am delighted to point you to Gareth’s blog*, where he has essentially channelled my rant from past years and a continent away. (Though, I confess, I never did come up with as clever and apt an analogy as he does with the clothing thing.)
The basic thesis: issues of right and wrong in language use are, pretty much always, relative.
I don’t think it’s a stretch to suggest that most linguists would accept Gareth’s position as pretty obvious. But there are vast swathes of people (even intelligent people who think about language a lot) who think very differently. Let’s hope his lucid prose will sway some of them.
[Update 2012: Gareth's blog sadly no longer exists. I won't delete this post, but I'm afraid without Gareth's content it loses much of its point.]