Hmmm, I think we'll have to agree to disagree on that one. I think resentment from a group that have been disenfranchised is understandable, while from the oppressive group it's pretty abhorrent. I don't think the "two wrongs makes a right" argument holds, because pushing back tends to be what effects change.
And I just don't think it's up to me or anyone else to correct someone's spelling or grammar, unless they want it corrected (in my case I do, because my own can be shaky). In fact I think someone doing so is petty-minded for one, and actually a bit of a bully, too, given context for most - though between two happy pedants, obviously it could be a joke or just a point of interest. I'd not do it because, well, it's a small-minded and prissy thing to do, IMO.
I actually find language fascinating - someone corrected someone else online a few days ago for misusing "disinterested" as "lacking interest" instead of "without ulterior motivation" and I was curious, so googled. And I found that the earliest known example of use... was for the disputed meaning. It's something numerous pedantic sites insist is a linguistic blooper, but both Merriam and OUD state it's interchangeable. And it's also a good example of language altering meaning over time. Personally, I find it comical when people use "literally" as an emphatic instead of literal, because the statements that arise are hilarious - "he was literally beside himself!" about a pissed-off footballer, for example. But I also appreciate that language is a living thing, and most people now use "literally" in that way, so really it's altering meaning before our eyes, and that's what language always has done. It's viral; it mutates. Which is me at a tangent; sorry!
I do find it frustrating when people post on MN asking for help for a problem but posting so badly it's genuinely hard to fathom what they mean. But I also get irritated when they're met with a lofty, "Sorry, can't read that solid block of text, especially without spellcheck!" because it's just so unnecessarily demeaning and, well, nasty - why post at all, if that's all you can say? And frankly, you can't leave class out of the equation here either, because the reality is that literacy problems are massively more likely, dyslexia aside, the poorer someone is. It's often a thinly-veiled way a middle-class person can put down a working class one, without other middle-class people pointing out the snobbery. Because it's ostensibly about grammar/spelling instead.