Refusal to allow investigation? According to these papers, their has been very extensive investigation with a largely null conclusion. However people continue to push the idea that intelligence is genetic.
A null result doesn't prove that intelligence is not genetic, it only says that whatever genetic components there may be have not yet been disentangled from other genetic and environmental influences.
Edit: Also, another HN commenter raised the possibility that the authors of the present study may themselves be biased (https://news.ycombinator.com/item?id=4257220).