I want to talk about one of my pet peeves.
Now, I'm not so stodgy that I insist the language remain exactly the same as it was in my youth. I just don't think that's realistic. The world is changing and language needs to change also, or we'll soon notice we can't verbalize our observations about the world. Slang and dialects are part of that, so that's not the type of thing I usually get upset about.
This particular pet peeve is this: "My co-worker that has red hair…" I hear this all the time, not to mention read it. In this example, 'that' refers to 'co-worker', so a person has just been referred to with a non-person pronoun. In my mind, 'that' can refer to sofas, cars, houses, and even animals. But when you are speaking about a person, it is far more respectful to refer to them as 'who'. It is acknowledgement that they are human. "So I said to my co-worker, the one who has red hair…"
I could be wrong. I don't profess to have any kind of high-level college degree in English. It just seems to me that if you are referring to people, you should at least acknowledge that they are people, and not 'things'. After all, what goes around comes around, right? Would you like to be called a 'thing'?