I am thrilled that KA exists. I have read Khan's book and recommended it to others. I don't see anything in this post about "discrediting" KA. I think the author is making a completely valid point and I hope that KA addresses it soon.
> Mr. Khan, you have a team of teacher advisors. If none of them can identify these gaps for you, you need to ask for help from the larger community (and then to reexamine your hiring practices).
> Or you could educate yourself (as we require of all licensed teachers) on what is known about how people learn mathematics.
Which of these contributed to his point? The whole thing is just entirely unnecessarily snide and personal. He has a simple and straightforward point that could have been explained in a concise and conciliatory manner, but he chose to use it as a platform to grind an axe. Also the "open letter to Sal Khan" title is confrontational linkbait. This is just not constructive.
Nobody wants to read a boring article about a better way to teach decimals. Sad but true.
Edited to add: the first quote is blunt, but not, I think, out of line. I do think I detect a bit of condescension in the latter two.
Do you have any other suggestions as to how the pedagogical flaws could be addressed, since Khan Academy keeps basing all its exercises on these flawed materials?