I'm unaware of flying dogs. To separate myself from people that believe in the existence of flying dogs, I don't describe myself as an anti-aerocanine. Rather, I review my experience with and knowledge of dogs and everything I've read about mammals, and I make a statement: "Flying dogs do not exist." If a friend were to say, "I believe in flying dogs" or "I believe that dogs have the physical capacity of flight," first, I would imagine that the friend is joking and if joking is eliminated as a motivation for the aerocaninite, I would make my exodus in the conversation.
Saying that a flying dog exists would require overwhelming evidence to support such a wild assertion. The aerocaninite would rightly bear the burden of proof if he/she were trying to prove the existence of flying dogs because there is factual evidence that denies his/her claim. The question "Why do you not believe in flying dogs?" to any rational person would be seen as completely absurd. The question "Why do you not believe in god/s?" is exponentially more absurd. Dogs can be studied. Dogs can't fly. Gods cannot be studied.
Also, the word Believe is a tricky word. Watch it closely.