Both have interesting personalities and each has unique strengths: Audacious Epigone is data-heavy on intelligence; Mangan's Miscellany touches on nutrition and investing. But these are topics that are better to learn about elsewhere, such as through peer-reviewed review articles on the topics. Some might say that intelligence is too politically sensitive to be discussed properly in these channels. That's just wrong, because there are probably hundreds of articles discussing the topic, plenty of academics have advocated for it, and they have been responded to by other academics in the very recent past.
Having read into the debate and worked a bit on the Wikipedia article, I don't think that Flynn and Nisbett have really been engaged properly by Rushton and Jensen. In the response to Nisbett's latest book, Rushton and Jensen resorted to technical jargon rather than proper engagement. Overall, yes, we know there's a gap between the races as shown by measures used to test intelligence.
In any case, whether there truly is a gap doesn't really matter. All that matters are the social implications. Does bringing up this issue and trying to convince everyone of it serve any useful social purpose? Rushton and Jensen have tried to argue yes. While it's debated, I strongly suspect that in 1969 Jensen tried to argue that the correct takeaway was to teach black people in a more rote manner (see Harvard Educational Review 39: 1–123). I can't see any useful social purpose, and I see substantial risk of racism, discrimination, and stereotype threat. The fact that someone would advocate such a thing despite the vastness of the unknowns, individual heterogeneity, and the imperfect information available to people in everyday life is morally despicable.
In 1969, we did not even know that lead caused IQ deficits in children. In fact, "we" didn't really know that leaded gasoline caused any health problems at all. By "we", I mean the general public, since occupational health scientists were well-aware of the health hazards of lead when it was first used (see Kovarik 2005). However, this brings up another point: these two bloggers, like many others of the "right-wing" crowd, do not seem to recognize the four-dimensional nature of the political compass. Would these people have opposed lead regulation? Some might think that is a straw man argument, but I hardly think it is a straw man to say that in the 1930s, these type of people would be the most strident of corporate apologists, as those who are self-described "right-wingers" are similarly corporate apologists today.
There's a general antipathy towards moving forward which is evident in even the label "conservative". And this is more than just a worded label. Those who use it to describe themselves take it to heart. These are often people who think that we can save the economy by simply drilling more and more holes in the ground. These are the people who have strongly opposed the abolition, as more than half of the country at the time did.
Despite my talk of the political compass above, I genuinely believe that conservative is a mindset - perhaps a genetic predisposition - which has been generally against every progressive (defined as a change which equalizes power among the units of a society) change in society, ever. An example from American History can be provided. Abraham Lincoln was an extreme liberal in his day. Seward, his secretary of state, almost won the Republican nomination but was considered too left-wing as he had been more open in his views toward abolishing slavery, and had also been a typical liberal spendthrift as Governor of New York. I have read that Abraham Lincoln ran on a platform of increasing federal power and government infrastructure investment. When the Democrat party began to become liberal, the conservatives swiftly shifted to the Republican party. Many are aware because of the Trent Lott incident that the infamous Strom Thurmond, a Republican Congressman who ran on a desegregation campaign, was originally a Democrat - but the hyper-racists have switched parties as conservatism has switched to the Republican party. And there they persist in their campaign to make sure that the productive energy of the world is used in making sure that the rich can have more luxuries, with a caveat that the lower classes can be helped through oil subsidies to the companies to which the rich own.