I can fully respect your input, but try selling this to the employer who's looking over an 18 year old's work application.
I don't care what it evolves to within (or in excess of ) a 100 years from now. What matters is what's currently being taught within our grade schools. What matters is here and now... and how our language(s) evolve in their future use is irrelevant to me.
Grammar and/or spelling errors are simple errors to fix, such as what Bethesda could be doing with their subsequent Data patches that are rolling out.
You make a good point about the social view of grammatical innaccuracies, but I do tend to think that this point is somewhat overstated. I have spoken to someone who is the head of the English Language & Linguistics department at a prestigious British university, and they have said that self-expression and eloquence are far more important in a personal statement than correct grammar - I don't even get penalised for "misuse" in the essays I submit here. And let's not get started on the fact that "correct grammar" is purely subjective. To boldly split my infinitives and end my sentences with prepositions is what I strive for!
I agreed with most of your post - particularly the L'academie thing - I have lived in France and I found one of the great issues with communication there, is that if you do not say the word absolutely correctly, people do not seem to comprehend what is being said (I had put this down to intransigence, but it happened when people were being nice too!). This is one of the reasons I love the flexibility of English. You don't have to have an exact pronunciation to be understood ... but I digress too.
I disagree that the OP should stop complaining - I think he/she makes a valid point, since the misuse of your/you're changes the meaning of the sentence. As I said, it's about balance. To substitute 'whom' with 'who', does not change the meaning.
Either way though, everyone is entitled to say their piece - in whatever manner they choose

I would argue that who/whom changes the meaning just as much as your/you're though. In fact, I would say it changes it even more. If you see an adjective or participle after "your", you know they meant "you're". If you see a noun you know it was meant to be "your". If, on the other hand, someone says "He bit her." in conversation and I reply with "Who?", I want to know who the man is. If I say "Whom?" I'm asking for clarification about the woman.
You said earlier that "bored of" irks you; how does "of" change the meaning from "with"? Many adjectives can take different prepositions, and because I hear "of" more than "with" nowadays, I probably say it more too. Familiarity will subconsciously change what you say unless you make a conscious effort to be different, but I don't see the point in that myself if it doesn't affect the meaning. You'd say "I'm free of him" instead of "I'm free with him", right? There, "of" is being used to mean "in regard to" (or "with regards to"

) and I don't see anyone complaining.
Still, what you say is true; prescriptive grammarians do still exist (those who prescribe and proscribe what should and should not be said), but I myself fall into the other camp. Descriptivism seems much more natural to me!