https://theeconomyofmeaning.com/2015/11/12/new-study-shows-r...
It's like https://xkcd.com/603/, except White Hat is is wrong on most accounts.
"You arguments are wrong because Flynn effect, and if this one is reversed then your arguments are wrong just because."
Everybody these days is a eugenicist in that they all support the idea of helping pregnant women give birth to health children by ensuring they are well nourished and given good medical support. The section of 20th C. eugenics that is controversial is the part that suggests that one section of society should have more or less children.
Here's a recent and fairly pro-eugenics survey of all the results they could find showing a reduction in IQ:
https://www.gwern.net/docs/iq/2016-dutton.pdf
And even they basically are only at the stage of saying "maybe there's a hidden trend, that's obscured by other trends moving in the opposite direction" (they think society becoming more abstract has caused a false rise in IQ, due to IQ tests measuring that socially taught facility with abstraction rather than raw intelligence, this may have disguised an actual drop in intelligence).
So maybe it does help to have a preconcieved cause to spot this hypothesised trend.
Regarding their hypothesis, it's kind of a philosophical question about whether you'd rather have a society full of uneducated bumpkins (not sure there is an english word for someone with raw intelligence but no education) with sharper reflex times or ability to discern colors, than a modern post-graduate who scores slightly worse on those tests but better on IQ. It's also somewhat unlikely that the former is going to be having less children than the latter, so they whole dysgenic thing seems to be on shakey ground.
Unless all the people I personally know are very unrepresentative of society in general I have a hard time believing that there is not a negative effect on IQ due to differential fertility.