My first instinct is to doubt that there is a connection, that the correlation indicates causation. But it does not seem impossible to me that the entire culture of “culture wars” in which people learn to distrust their fellow human beings, suspecting that they are undermining the fabric of society and all that is good and true (by being evolutionists/Republicans/atheists/gays/Christians/Communists/Chick-fil-A customers/whatever else), fosters dehumanization of others to an extent that does indeed have an impact.
Or maybe it is the fact that some people are taught at home (or at church, by Rick Warren for instance) that if evolution is true, then we have no reason to be moral. When those people discover that they we lied to and evolution is indeed true, are they not likely to assume that the second part also applies, and that there is no reason to be moral? It becomes a tragic self-fulfilling prophecy
But then again, the correlation may just be a coincidence. What do others think?