There’s an old debate over whether that as a relative pronoun can refer to people. As far as I’m concerned, of course it can. The usage is fully standard and has been for centuries. Briefly: that can be used to refer to people or things, which refers to things, and who(m) is reserved for people and animals:
the house that she lives in (or which)
something which has long been disputed (or that)
people who fuss over relative pronouns (or that)
Tabby, whom I adopted as a kitten, is four today. (or who)
Note, though, that that and which are less interchangeable in AmE than they are in BrE. (The Merriam-Webster Dictionary of English Usage has a helpful history.) Sometimes a distinction is made depending on whether an animal has a name: who for animals with names, that or which for animals without names. This is the AP Stylebook’s advice.
AP style does not allow that to refer to people, and neither does the New York Times Manual of Style and Usage.* This is style advice, which is very different to grammatical correctness. For the latter, we consult works more authoritative than style guides. Bryan Garner’s Dictionary of Modern American Usage contains the following note:
That, of course, is permissible when referring to humans: the people that were present or the people who were present. Editors tend, however, to prefer the latter phrasing.
Which brings us neatly, our sense of irony to the fore, to a recent edit in the NYT. Garner wrote a commentary in its Room for Debate on the need to reform legal education in the United States. His article concludes as follows:
the future of continuing-legal-education seminars for the practicing lawyers – the kind whom I teach – looks very bright indeed.
But this is not what he wrote. That, not whom, was the relative pronoun in Garner’s original text. Apparently an editor “fixed” it before publication, “thereby changing the sense entirely,” as Garner remarked. Thus:
the future of continuing-legal-education seminars for the practicing lawyers – the kind that I teach – looks very bright indeed.
The parenthetical text between the dashes – “the kind ___ I teach” – was meant to refer to the seminars Garner teaches; after editorial interference, it referred to the lawyers who attend them. The edit was worse than unnecessary.
If practicing lawyers were the antecedent (i.e., what the relative pronoun relates back to), that would be grammatically fine, though it goes against NYT style. But it would make more sense in that instance to use whom, since this precludes the possible ambiguity: whom could refer only to the lawyers; that could refer to either the lawyers or the seminars. So a sensible reading would connect that to the seminars.
Presumably the two readings were not noticed, just one mistaken one, and the edit was made automatically to accord with house style. If there had been any doubt, the editor would surely have consulted a colleague, or some reference books, or if necessary the author himself. Maybe multiple editors agreed to it.
Regardless, the change was made and published and it undermined the sense of the text.
If I were editing prose from someone who writes dictionaries of law and English usage, I would expect the prose to be smooth and punctilious, and I would not introduce changes lightly. It’s a minor matter, but not an insignificant one: the “typographic oath” for editors is to do no harm.
* I don’t have a copy of the NYT manual, but I trust Merrill Perlman‘s report at the Columbia Journalism Review.