Well because you basically accused most people of being eugenicists simply for believing something that is most likely true and clearly implied a strong position that you are now retreating from. It's clearly an incendiary one-liner where previously the conversation was not so.

> The researchers who look at those things seem to be the ones telling us that the relationship between intelligence and genetics is complicated and many, many non-genetic factors are in play, no

There are massive biases in academia that encourage researchers to hedge results like this. When you ask anonymously, the answers & beliefs are clear.

> Snyderman & Rothman (1987/1988) — mailed survey to ~1,020 academics; 661 replies. Experts overwhelmingly agreed that IQ has substantial within-group heritability, and among those willing to give a number, the average estimate was ~60% for U.S. populations. Also https://pmc.ncbi.nlm.nih.gov/articles/PMC4804158/ which is going to be a lower bound because it focuses on international differences.

Adoption studies pretty clearly upper bound the amount that these complicated non-genetic/non-prenatal factors can be causing differences in tested adult intelligence among Americans.

> I'd politely ask you to refrain from insulting my good faith.

Again, you started your entry into this conversation by leveling accusations of eugenics. The responses you get are going to be tinged by that.

> how you come up with that clear of a statement about smart parents and their non-externally-influenced child, how one would approach that as a research question/design

Adoption studies can provide an upper bound (excluding pre-natal environment). Also GWASs paired with mendelian randomization can provide a lower bound.