“Grammar Nazi” is a term widely misused by folks on the Internet to refer to anyone who takes umbrage at illiterate abuse of language. It is a term of derision mean to the shield the user’s ego, usually after their own subliterate (or downright illiterate) abuse of English. Seriously insecure people are “offended” by others’ abuse of English being corrected.
Grammar~Syntax?Structure, logic, reason, all affecting the clear transmission of meaning. The more “noise” in the transmission, the shallower and less meaningful the transmission.
Phonemes (and their analogs in print) are just noise absent syntax and semantics.
Syntax: structure (99% of grammar). Affects semantics.
Semantics: meaning–the transmission of which is the sole justification for language.
“Now there abide these three: phonemes, syntax, and semantics; and the greatest of these is semantics.”
Where phonemes (and their analogs in print) are poorly transmitted (poor pronunciation or poor spelling), meaning is less well transmitted. Where syntax is garbled (spoken or in text) meaning is less well transmitted.
If these are important when speaking or writing in a “foreign” language (and they most CERTAINLY are!), then they are just as important when speaking one’s own, “native,” language.
Nazism does not apply, since fascist socialism has no place in any of these things.