The real problem is not the particular study by Kennedy et al. It is an important and intellectually honest effort to address a difficult question. Although significant, the critiques listed above are difficult to address with available data. The more people cavalierly cite academic studies, the more the public will believe that scientific studies can not be objective. When citations do not ring true, the public begins to believe that scientists are, like lawyers, hired guns willing to argue anything.
Increased cynicism makes genuine reasoned dialogue more difficult.