Apparently its use was first branded unacceptable by a female grammarian.
If any single person is responsible for this male-centric usage, it’s Anne Fisher, an 18th-century British schoolmistress and the first woman to write an English grammar book, according to the sociohistorical linguist Ingrid Tieken-Boon van Ostade. Fisher’s popular guide, “A New Grammar” (1745), ran to more than 30 editions, making it one of the most successful grammars of its time. More important, it’s believed to be the first to say that the pronoun he should apply to both sexes.
A interesting article, even though it does employ a rather suspect definition of ‘feminist’. The authors seem to think that a move back to ‘they’ is pretty much inevitable, and they seem just fine with that. One suspects William Safire will not be well-pleased with this column published while he was on vacation. (For those who want more on this history, there’s an excellent paper by Ann Bodine in Cameron’s _The Feminist Critique of Language.) Thanks, Mr Jender!