Frank Bruni, in an op-ed for The New York Times:
Instead of saying “people who,” Donald Trump said “people that.” Marco Rubio followed suit. Even Jeb Bush, putatively the brainy one, was “that”-ing when he should have been “who”-ing, so I was cringing when I should have been oohing.
It’s always a dangerous thing when politicians get near the English language: Run for the exits and cover the children’s ears. But this bit of wreckage particularly bothered me. This was who, a pronoun that acknowledges our humanity, our personhood, separating us from the flotsam and jetsam out there. We’re supposed to refer to “the trash that” we took out or “the table that” we discovered at a flea market. We’re not supposed to refer to “people that call my office” (Rubio) or “people that come with a legal visa and overstay” (Bush).