(In case its not clear, I'm mostly agreeing with you. :)
“Mr. Khan stands exposed as possessing a historical perspective steeped in academia’s standard issue, postmodern, left-leaning narrative of cultural relativism, multiculturalism, and moral equivalence.”
And then this:
“In a sense, that’s what Internet personalization filters are already doing, creating an echo chamber where we only hear what we already believe. We can’t think about what we’ve never heard of.”
And here I thought coherence was always a fashionable accessory.
Right now, it looks like you're saying that the first quote's adjectives describe a meta-viewpoint that need not be examined as a viewpoint in and of itself.
I might have read too much and falsely concluded that the author is against Khan’s “historical perspective steeped in academia’s standard issue, postmodern, left-leaning narrative of cultural relativism, multiculturalism, and moral equivalence.” The OP might be neutral about that, and simply exposing the necessity of balancing Khan’s against a different narrative¹. If so, either his articulation was obfuscated by the choice of words or I need to practice my English a lot.
¹. Never mind the fact that this rarely occurs in real classrooms.
Instead he chose to bash a popular figure. Probably because it gets hits on his blog, but who knows, I'm cynical.
There are multiple and various reasons for studying history, whether this is articulated clearly in everyone's mind or not. Establish a baseline cultural past, instill moral values (ex. glorifying Person X's accomplishments), predict future results of actions, and entertainment are reasons that also spring to mind just off the top of the mind.
If history is being taught simply to teach decision-making skills, then using a case study format would be one possible way to improve the current teaching methods.