Elizabeth Landau writes:
Consider the sentence "Everyone loves his mother." The word "his" may be seen as both sexist and inaccurate, but replacing it with "his or her" seems cumbersome, and "they" is grammatically incorrect. […]
It turns out that an English speaker's mind can't instantly adopt an imposed new gender-neutral system of pronouns, linguists say. A sudden change in the system of pronouns or other auxiliary words in any language is very difficult to achieve.
Except that it isn't a problem any more. Mark Lieberman over at The Language Log blog (where distinguished linguists like Mark Lieberman hang out) writes:
Language Log is here to reassure Ms. Landau that the problem has already been solved. Singular they is supported not only by the usage of today's youth, but also by historical scholarship, psychological experimentation, government regulation, and divine inspiration.
[For a more complete discussion of the historical issues (both descriptive and prescriptive), take a look at pp. 51-53, 414-416, 662-664, 666-667, 860, 901-903, of Merriam-Webster's Dictionary of English Usage.]
So not just isn't it a problem NOW. It's NEVER BEEN a problem. So all those people who've corrected me for using "they" as a singular pronoun (and they know who they are) can just POUND SAND! So there!
Lieberman quotes Ben Yagoda who quotes Shakespeare: "God send everyone their heart's desire." and The King James Bible: "In lowliness of mind let each esteem others better than themselves."