As someone who has been a teacher and trainer of various kinds, removing your own bias from your teaching does not come naturally or easily. So I think the points made (while exaggerated) have at least a kernel of validity. However, ranting on a blog is not a productive response. Instead, I'd document them as constructive criticism and send them to Mr. Khan directly. I've got to believe that anyone who is passionate enough about education to put the Khan academy together in the first place is also willing to hear suggestions on improvements.