HBD, AGW denial, and intelligent design are all similar in two ways:
1. All are against the status quo.
2. All have a large group of ignorant people who want to believe in them.
The big difference is that HBD has a significant portion of experts taking it seriously. There is an additional difference I have noticed in how they present themselves. HBD usually tries to minimize the most incendiary of its claims, often they are presented cryptically or in apologetic tone.(“I wish this wasn’t true but it is”) For instance, The Bell Curve had only a single chapter about race differences, though the media coverage overwhelmingly focused on it. With HBD, the title and book description is usually tamer than the contents. With AGW denial and especially intelligent design, the opposite is true. The title screams “Darwin Was Wrong” or “Climate Science Disproven” even if the claim is only “Darwin was right about most of evolutionary history but not abiogenesis” or “global warming is occurring and man-made but the rate of heating will be half of mainstream estimates.” This tells me that the intended purpose of these books is not to persuade fence-sitters of the truth of the claims, but to sell books to the large number of ignorant true-believers looking for a science-y justification for their beliefs.