There are none so blind as those who will not see.
Knowledge is a dangerous commodity. It erodes institutions, power structures, and world views. That's why the fiercest battles of anti-science are fought on behalf of churches, industries and other power structures. Smaller scale interests have their own territories to defend though, and scientists are not immune to the temptation to cast some studies into disrepute because they don't approve of the consequences that they fear might flow from them. We usually find, though, that the head in the sand approach is mostly just disadvantageous for those who choose blindness.
Many kinds of cultural analyses have been targeted by the advocates of the "blank slate" view of human nature, but none more so than IQ studies. IQ tests were originally designed to classify degrees of mental retardation, but they have continued to proliferate in use because they are one of the most powerful predictors of achievement in an enormous range of employments from science and high finance to professional football. Unfortunately, they also have been put to use by racists and eugenicists of various stripes. Thanks to the attacks of various blank slaters, led perhaps by the late Stephen Jay Gould and Richard Lewontin, IQ studes became so disreputable that they were mostly left to cranks and racists.
One trouble with intelligence (and hence IQ, which purports to measure it) is that it's bound up so closely with our self image. We call ourselves H. sapiens after all.
Like the (perhaps apocryphal) bishop who refused to look through Galileo's telescope for fear that he might see something that would damage his faith, the IQ denialists prefer to choose blindness. The main Satan they fear to find there is racism, and there is some hazard of that, because most comparative IQ studies do show racial correlations. Of course, in the absence of systematic study, all we have is vague hints as to either the reality or permanance of the causes.
That's ultimately a shame, because suppression of research has merely prevented us from learning the causes of IQ differences. The knowledge of racial differences in IQ has hardly been suppressed, but the widespread refusal to consider it has done more to feed conspiracy theories and racism than to prevent it. There is plenty of evidence to suggest that both environment and heredity contribute to IQ, but how and in what way is nearly entirely unknown.
This particular Terra Incognita is likely going to be understood sometime, by somebody. Suppose we do find that higher IQ is closely associated with certain genotypes. What then? The most likely thing in the future is not some kind of genocidal murder program, but rational therapy, based on genetic medicine. Echoes of Brave New World? Yes, but it's coming, and we ought to prepare to deal with it.
We have some experience with societies that choose denial over reality. Reality has it's way of asserting itself.