I am going to throw this out here... I believe that mostly every post I read, there are a multitude of errors, and I feel like I am getting dumber with each passing day. Not that it really matters, but it might to some people, I don't want to make the same mistakes, and start misspelling words that otherwise I would have known. So please people, have some consideration, and don't look like an idiot! It will do everyone a favor to use correct grammar.
I agree with you. Poor spelling and grammar can sometimes make reading too tedious to be worthwhile. I sometimes get confused about what people are actually trying to say or ask, and in those cases it really does make a difference. And it's often not evidence of poor education so much as carelessness.
Sometimes an OP will do such a bad job at posting a question that I think to myself, "Why do you think anyone should care about helping you if you didn't care enough to think through asking your question clearly?"
Like I said, though, I don't think it's about uppityness on one hand or education on the other. Knowing the difference between 'there', 'they're' and 'their' doesn't require a Ph.D. It requires a 3rd grade education and just a tiny bit of concern for how you present yourself to others.
My opinions:
Grammar police on internet forums are unnecessary, but presenting yourself clearly is an important sign of respect and consideration for the people who will be reading your posts.
I don't think the OP was being rude or acting as grammar cop by calling attention to a general phenomenon. If it had been directed at a specific person or post, though, it might have been rude.
Btw, the following quote contains a comma splice:
Not that it really matters, but it might to some people, I don't want to make the same mistakes, and start misspelling words that otherwise I would have known.
You're not supposed to use a comma to separate two complete thoughts. A period, not a comma, is called for after the word 'people'. The comma between 'mistakes' and 'and' is also unnecessary. [See? Now that was rude. Sorry, OP.]