I am skeptical also. First, the baby had to be unclothed and unprotected. Second, how did the dog know there was an opening to penetrate...dogs are attracted to scent, not feces. If anything, this dog was exhibiting learned behaviour....take it from there. Third, never leave a large dog unaccompanied with a baby or child...never...never....never....
This story sounds like a liberal media story to jump on the bandwagon to outlaw mean pit bulls..Like you, my money is on some lies being told or just a pure unadulterated fairy tale.