Every serious student of English should watch the BBC's most-excellent series The Adventure of English, especially the episode Speaking Proper. (Hooray for the use of a flat adverb in that title!)
That episode, and actually the entire series, will help you to understand the folly of believing in a fixed, standardized English where rules of PUG are carved on stone tablets, stored in a golden tabernacle somewhere in the hallowed halls of Oxford. The episode chronicles the 18th-century post-Enlightenment intellectuals, who, after rejecting religion, found themselves bereft of a means for controlling others' behavior and setting themselves apart from the vulgar masses. So they attempted to replace the canon of a "true" religion with that of a "true" English language. (That's my interpretation, not the BBC's.)
Naturally, they failed, as did France and Italy before them. Even the esteemed Samuel Johnson gave up on the idea of a standardized English well before he'd finished his dictionary. I think it's telling that the group that gave these crusaders the biggest fits were the upper classes, with their penchant for playing with the language, inventing new words and phrases, and generally not giving a flip whether anyone thought their English proper or not. And, of course, the uneducated lower classes couldn't be counted on, so it was left to the middle classes to carry on the crusade for "proper" English—basically, the intellectuals and those wanting to be thought of as intellectuals.
Don't get me wrong; there are rules. But the best communicators know that rules can stifle better communication. A grammar bully (or grammar nazi, as it is often called) is one who insists on you following a rule of their choice without understanding, or even caring about, the rationale behind it. Rules is rules.
But I say, rules are the training wheels on your development. If you're going to be a good communicator, at some point they have to come off. And if you insist on a rule, you'd better be able to explain to me why that rule is necessary.*
Watch Speaking Proper for some insight into our attempts to fix and standardize our language and the concomitant birth of English grammar bullyery.
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* Or brace yourself for a good claquing.