I look at it from the perspective of language being a tool to help us convey information. It needs rules, like any standard. But it also must be flexible enough to allow the expression of as many ideas as possible. (Think about Orwell's Newspeak as the opposite of this.)
I don't actually see any fundamental harm if someone says "He yelled at Brian and I," although that does break the rules as you and I understand them, and I certainly would not say it myself and would mark it on a student paper. I think what is happening in your examples is that linguistic competition is stripping out that which is unneeded. Eventually, people may use objective and subjective pronouns interchangeably without anyone caring. But at any moment in history an individual using the King's English lets other people know that he is serious about communicating effectively, so it is important.
But there is always linguistic change. No one says "thou" and "thee" any more. Few know the meaning of the adjective "ruth" anymore, even though it is obvious once we see "ruthless." OTOH, "Google" as a verb is now growing in usage. So as I said change per se doesn't bother me. What bothers me is people whose English is so incompetent that they can't communicate what they wish to communicate. They are the people who most need to get drilled in the rules.
BTW, for language nerds, a really cool new tool is Google Ngrams, which allows the user to trace changes over time in the use of any phrase in books that Google has scanned. For example, you can enter "if i was going," which most of the time is probably a misuse of the subjunctive. This phrase has been getting more popular since the early 1960s, which I think will accord with the belief of many Freepers that this was when civilization began to come apart. :)
Hmmmm....hopefully Economics is a more practical subject than English and garners more respect. Having been an English major (at UC Berkeley, pre-campus riots) there is nothing more ridiculed than an English major. But, we did learn proper forms of speech and writing and learned when it was permissable to break the rules, such as starting a sentence with But.
However, I am dead serious. When do you abandon those forms we learned in the 1950s? I NEVER hear, nor see, “whom” used any more. Nor, “were” in the subjunctive. Nor, “nor”. Nor, the appropriate use of the objective and the subjective personal pronouns.
About 10 years ago I re-entered college to earn a Business Management degree. The course was created for working adult students, and we often were required to work in groups. I appointed myself as the language monitor, pulling together our group projects and making sure that we used the proper forms of end notes, grammar, spelling, margins, etc. Otherwise, we would have never earned our A grades. My group members (all much younger than I) just didn’t care; and neither did some of our professors. ‘Tis a pity!
So wordophiles, I frequently see this choice of wording, and I'd like to ask "those a you" (<---- I see this a lot, too) to comment... Is it:
"What bothers me is people whose English is so..."
- or -
"What bothers me are people whose English is so..."
and why.