This article begins with a number of false arguments and devolves into mere skim-worthiness thereafter.
While words like "each man" and "everybody" are grammatically singular, they are semantically plural, so of course, plural pronouns would accompany their usage stretching back to the emergence of this pronoun[1].
If we are arguing for the age of a pronoun, then surely we should be arguing in favor of the much, much older singular, neuter "it"?[2]
The article continues on to complain about 18th century grammarians (which is valid) but if you don't like prescriptivist grammarians, then..
Stop telling other people how to speak.
[1]: Originating from the Old Norse plural pronoun "þeir" which displaced the native Old English "hīe", still found in some regional UK dialects.
[2]: Originally with leading 'h' and thus "hit". Still found in some American English dialects, cf. "hit wasn't me!".
While words like "each man" and "everybody" are grammatically singular, they are semantically plural, so of course, plural pronouns would accompany their usage stretching back to the emergence of this pronoun[1].
If we are arguing for the age of a pronoun, then surely we should be arguing in favor of the much, much older singular, neuter "it"?[2]
The article continues on to complain about 18th century grammarians (which is valid) but if you don't like prescriptivist grammarians, then..
Stop telling other people how to speak.
[1]: Originating from the Old Norse plural pronoun "þeir" which displaced the native Old English "hīe", still found in some regional UK dialects.
[2]: Originally with leading 'h' and thus "hit". Still found in some American English dialects, cf. "hit wasn't me!".