The purpose of PSSI is to educate the public about the scientific facts regarding the hypothesis of Darwinian macroevolution.
Immediately below this statement is a list of "resources" consisting of a handfull of well-known creationist books and DVDs, but not a single scientific paper, no Origin of Species, nothing by Dawkins, or Gould, or Maynard Smith, not even a single biology textbook. How's that for scientific integrity?
Amusingly, they apparently don't have too many members and had to resort to padding out their list of signatories by listing the names three different ways. And by including dentists. ;-)