If you are not an able bodied person, then a dog may take that as a sign to attack. Though, it will only attack if several of the other factors are in play. So if you ARE a bad dog owner, AND you are alone with your dog, then things may get interesting.
I am at home with my dog alone all the time. I have no fear of her, she may even try to save my life if the situation comes up.
If I had neglected or mistreated her, or intentionally trained her to be vicious, then yeah, it may not be a great idea to be alone around her.
Most of the time these stories that talk about not having an able bodied person around is talking about a child, disabled, or elderly person, who are unable to fend off an attack. If a dog came at me, trying to do me harm, I am pretty sure I would get the upper hand on it, though it is quite likely that I would get severely injured in the process. If I was not able bodied, then it is quite likely that it would be able to continue the attack, and I would not be able to defend myself.
Not really that fucking dumb assed, or even stupid assed point. If you are not able to defend yourself, stay away from strange or ill-mannered dogs.