I so agree. I get this a lot, and I'm a professional writer - ie people pay me to write well, and ensure that other people's words read well! But it never ceases to amaze me how many clients will change what I've written, in a way that now makes it grammatically wrong / ambiguous / illogical in context / repetitive or contradictory of something said elsewhere / tonally wrong...
You get the idea. There's a lot that can go wrong with writing. That's why writers sweat over every word. And you can't defend yourself, because then you look precious, or a grammar nazi, or a PITA holding everything up over trivia, or a privilege-pulling bully.
The irony is, the ones who really care about language are generally the least status-conscious people in the room. We just want to get it right, for all the reasons you mention @Vroomfondleswaistcoat. The last thing we want is to get to the point of 'Because I'm right and you're wrong'. Obviously if it comes to that, the battle's lost.
But we'll always defend our case because for us meaning matters. Humans have this brilliant gift of language and we want it be used as intelligently as possible - to share information, to entertain, comfort, prompt thoughts and feelings, and loads of other stuff. Most of all, language connects us with each other.
To do those complex things it has to be clear to the majority of people. And collective wisdom over the centuries has passed on ways to make that happen - through grammar, syntax, spelling and punctuation etc.
Language is always changing of course, with time, geography - and more recently in human existence, with technology. But if it changes so much that clarity of meaning becomes irrelevant, then I think we are passing on a terrible legacy to our children.
Here endeth the lesson ;)