Intelligence does not always aid in the search for truth. For those without good character, intelligence often merely enables the invention of sophisticated rationalizations for one’s prejudices. Intelligent people often find themselves able to win any debate they enter through superior mental agility, and consequently never bother to inquire seriously into the facts or arguments pertaining to the issues about which they believe themselves to be knowledgeable.
You can see this phenomenon in this xkcd cartoon:
The self-rightous character points out that despite our dysgenic fertility patterns, average IQ is increasing (the Flynn effect). This is true, but ignores the difference between genotype and phenotype. Take a parallel example, replacing intelligence by height. Suppose we knew that short people were reproducing at higher rates than tall people. Since height is largely genetic and heritable, we could conclude that people were getting shorter on the level of genes. If average height were increasing, we could conclude that some other factor was in play – improving nutrition, perhaps. Since such environmental benefits can’t continue to increase height at the present rate indefinitely (no matter how good your nutrition you can’t make yourself a foot taller) the effect will eventually peter out, and the decrease in height determined by fertility patterns will set in.
The same applies mutatis mutandis for intelligence.
(The turn to moral and social decline in the latter panels is not just a non sequitor, but also completely wrong. More harm has been caused by panic over decline than by decline itself? Dude… ever heard of the collapse of Rome? Building technology and sanitation didn’t reach Roman levels until the 19th century. Or how about comparing Greece in classical antiquity versus today.)