I believe allergies to dogs are far more common than people who need to take a dog on an airplane.
My position is this. If you need that dog to see for you, that's an acceptable reason. If you need that dog to help you face life, F*** you. Grow up. Put your big girl panties on and quit making everyone else put up with your unnecessary indulgence.
The man might be lying about a dog allergy, but there are a lot of people out there that actually have them, so I would give him the benefit of the doubt over someone who brought a dog to make them feel better about life.
Again, seeing eye dog wins the contest. All other animals do not.
But,but, but... What about my seeing eye wolverine?