> It's not clear what technical content this post has.

Indeed. The post is a big exercise in strawmanning (and of course ad hominem but I am willing to forgive it because it adds entertainment value). Andrew Gelman (a well-known statistics expert) dunks on some guy because he dared to defend a shitty graphic and "made a statistical error". Which is kind of unfair, because he didn't do any statistics. Of course when our brains see some curves they can't resist the temptation to do some statistics on their own, but bad dataviz is a different sin than bad statistics and should be treated as such.