Hmmm. This is an interesting counterargument. I appreciate it. I’ll have to chew on this a while.
My thought process as I made the argument that I did was this: I was thinking of the numerous writers (especially on the web) who are posturing themselves as experts. When someone does that, but then proceeds to write clumsily, I have a hard time believing them, and a hard time giving them my attention. Looking back at what I wrote, perhaps it would have been better put a different way — more about posturing, and less about grammar and spelling in and of itself.