I keep seeing people make this somewhat new mistake over and over again lately: they say that in reference to people or a person. So instead of saying, “he’s the person who wrote that grammar Nazi entry,” they’ll say, “he’s the person that wrote that grammar Nazi entry.”
“Oh those are the people
that who wrote that song!”
There’s a whole special relative pronoun for when you’re referring to humans: we call it “who.” It might be the cat that shat on the carpet but it’s the person who has to clean it up.
Yeah, blah blah blah, language should be descriptive and not prescriptive yadda yadda yadda. Go too far down that road and you have words that end up meaning two completely opposite things (the millennial definition of “literally”), words that are written as opposites that mean the same thing (regardless and irregardless, flammable and inflammable), or the most horrific grammar stupidity of modern times, grocers’ apostrophes!