oldfag here, lurking 4chan since 2007
Racism has been a part of 4chan since it's inception and it's always been a very difficult problem to remove that's gone through multiple stages or phases. Don't let people try to tell you it's welcome here. It's always been against the rules
>>>/global/rules/3 (even if Hiromoot doesn't enforce it enough) and it's been such a huge fucking problem they even had to delete some boards in the past to combat it
For a while they were content to sequester themselves to "containment boards" which people knew to avoid, but since 2016 they became extremely emboldened and seem to be doing some sort of Manifest Destiny thing where they "red pill" every board, which is just another way of saying their end goal is normalization of racism on every board. My intuition tells me it was likely some white nationalist group familiar with 4chan that started doing this shit, but for the most part they have succeeded, and now have turned blatant racism into a form of acceptable trolling.
To answer your question, talking about IQ and how it relates to racism is the ONLY way they can talk openly about racism and avoid jannies and mods from taking action. It's just barely within the limit of being /sci/ related so as to avoid moderation. Ergo, they spam the fuck out of this board with it. Again, some people will say they're only doing it to troll cause it's funny, but they're still being "useful tolls" for literal neo-nazis. That's like saying "i was helping hitler cause I thought I might get a giggle" Also, neo-nazi's DO lurk here. They're pretty shy about showing themselves but I've had the pleasure of outing a few of them into openly admitting. Expect them to be lurking this thread and try to defend themselves.