Of course, grammar nazis are bad.
People who fix a single thing aren’t grammar nazis to me at all. Why should we stop having teachers and correctors when we aren’t school kids anymore? It should be handled well, sure, I don’t bother with it myself anymore (I was a horrible kid, I always fixed the grammar errors of a penpal but it hurt me to read those, of course I tried to protect myself. I am not nearly that sensitive now, I know what really problematic things are and I like to give advice to people who ask for it, they are pretty thankful and that feels nice. I just understand people who still wish to make things better.)
Of course it may matter if one can’t know the langage well (it still irrelevant if it’s a 2nd language or not, well there’s correlation but I always liked the special cases one may be bad with sarcasm in their own language especially online and tons of people spend years in countries with a different language) but it was just grammar! That’s easy to learn as a 2nd language, sometimes I think it’s easier than being an ignorant native speaker (writer…).
Of course, being a weak language user due to little practice is very different, I only expect near perfect grammar from those as it’s super easy to look up and if they didn’t learn the word, they probably won’t use it… {Okay, okay, maybe they have bad memory or something. I don’t judge them if they are worse, I just expect them to be good at grammar…} I usually think my style is bad and I repeat words and so on (not like I am so great at my own language… my grammar is great and I know many words but I am no high-level language user like a good writer or poet) but I am pretty confident in my grammar (expect tenses but I usually ignore the difficult ones, it’s not like they are that important, my own language is fine without those, after all :D).
Erm, sorry, I could write whole novels about languages, it’s a fabulous topic!
And yep, certain things are tricky. I know the meaning but sometimes I don’t know how EXACTLY vulgar is something… when I talk with an Australian… (But it’s probably slightly different for different people at different places.) Being consistent is probably tough, I probably mix the 3 main English style (mostly US and UK, I know little Australian)…
We people are different so we never can fully understand others… We always use the same language a bit differently, our attitude is different etc.