@Letty,
Letty, I live in a part of the country where usage is extremely flexible. Plenty of people I know use phrases like "He ain't got none." And, quite probably, if I, who was for 30 years and English teacher, said "He ain't got none," no one would blink. I like high-tolerance areas. What would Wittgenstein say about the meaning of "He ain't got none"? I THINK he'd would have said the meaning was clear, despite double negative.
When I was in fourth grade, and my teacher, Mr. Spicer, was showing us how to diagram sentences, he insisted that "who" was used in relative clauses that refer to people and that "that" was used in relative clauses referring to everything else. I used to rock his world by using "who" in reference to animals, because we people are merely fancy animals.
I agree with you that grammar arguments are usually boring--unless you're working on a problem in logic or drafting a treaty.