Careful. Dr. McWhorter is relaying "the going idea" here to establish context. He's not espousing that view -- he sees texting as fingered speech, not writing. Or are you objecting to a perceived disparaging of graffiti?
I am not actually saying that the author is pushing forward this sort of thinking, but I do think that the author is wrong in saying that this is "the going idea" as I have never heard that comparison before. My objection is to this common idea that graffiti is "low-art" while something like poetry actually seems much more damaging in terms of proper english usage, yet is regarded as "high-art" (historically). I simply fail to see the connection between texting and graffiti and it struck me as odd that this could be a commonly held belief.