Here is a Piece from Psychology Today.

Plante casually claims that religious people are "better citizens" and "behave better." And without citing any sources, he tells us: "Research has consistently found that religious people are less likely to engage in criminal behavior, marital infidelity, alcoholism, unprotected sexual activity. . ."

In other words, according to Plante, if you're not religious you might be a good person, but on average you are more likely to have these undesirable characteristics. This is a bold assertion that, of course, immediately puts secular individuals on the defensive. (Just imagine if the same claims were made against any other minority group.) It is precisely claims like these that lead to many Americans having an unfavorable view of atheists and other nonbelievers.