You can doubt all you want, but take my word for it, it happened. I spent most of my time in Manila or Olongopo, and I would certainly have no reason to make up a lie about the subject.
A quick Google search indicates that Dog is "what's for dinner" in the Phillipines.
http://en.wikipedia.org/wiki/Dog_meat
http://www.google.com/search?hl=en&sa=X&oi=spell&resnum=0&ct=result&cd=1&q=philippines+eat+dog&spell=1
I asked my wife who was also there and plugged in pretty good. She doesn't remember any dog eating either,especially not as a common occurance. Someone posted a wikapedia article that says it is part of some religous ritual.
I'll not go further than saying I have lived in the philippines and worked much of my adult life with them and never heard of the practice.