Yeah, it's something I've noticed. if you base your decisions on what to believe entirely on the quality of grammar used by Internet supporters, you end up with the skeptical position being overwhelmingly convincing.
Well, I think of it this way: if you're not concerned about the details, the little things, the picky stuff, why should I trust you with the big things, the things that really matter? Like your arguments?
If you've read enough, learned enough, and explored enough to at least have some grounding for your opinions, wouldn't your writing reflect that? Maybe you haven't read much, explored much, or learned much. Maybe your opinions reflect that, as well as your grammar and spelling?
If you care enough to create a post, don't you care enough when you're done to go back over it, examine it for flaws, errors, maybe even read it aloud, as written, to yourself, before you hit "send?" You know: maybe raise your credibility points a little?
Look, if you don't care, you don't care. But in that case, when you make it so obvious, you can't expect me to care, either.
(Should have used the neutral "one," instead of "you," but am too lazy to recast, so take it as given, please.)