Grammar Police

Someone posts an article on my Facebook page: Is it rude to correct people's grammar, and I replied:
You betcha, but that ain't gonna stop me...however, ya picks yer battles.

FWIW, said author has it all wrong, it's not about being an academically fixated Nazi Grammar Jerk Who Need a Hobby. It's more like being OCD. It's genuinely painful to see written mistakes. And I'm dyslexic, so, when there are typos, my eyes get all tangled up in the syntax, and I can't comprehend the sentence. Really.

OMG, she's equating it all with wanting to be all loved and cuddly? Barf. Beware, Coddle Police at work. And then she has the audacity to say that the grammar police shouldn't have a leg to stand on, because "Grammar is a notoriously fickle and changing field." What are we, Sir Gawain and the Green Knight?

Yeah, well, no matter how much language evolves, your equals you're; and it's equals its; and there, they're their are all one and the same. No. Not. Never. Nohow. It's good to know the grammar rules, first, in order to break them.

And then she lets us off with a slap on the wrist, and a warning. Grammar Police beware? What's with that? Caveat emptor? Pah! I say, a pox on her house. Methinks she protests too much.

Is it rude to correct people's grammar?