reality, is it irresponsible of me to have a guide dog then? He is a big dog after all. 
For those that judge the breed, there is no evidence that certain breeds are more agressive than others. None. In fact statistically in this country more people are bitten by golden retrievers than any other breed. But that doesn't mean that retrievers are more agressive; it simply means that more people own them than certain other breeds.
Yes dogs are animals and we should respect them as such. It is however very rare for a dog to simply turn and attack someone without provokation unless that dog is specifically known to be agressive. In almost all cases where children have been killed by dogs in the past five years the dogs have not been the much-loved family pet but have been there for guarding purposes/have been kept outside/none of them were actually in the child's home but belonged to relatives and the attacks happened in the dog's home.
It would be irresponsible to have a dog that you couldn't control i.e. a rottweiller could quite conceiveably weigh as much as me, so were I to own one there's a chance that if he decided to make a break for it I would not be able to do anything about it. But that doesn't mean that rottweillers are habitually agressive - yes they can be, but equally there are many rottweillers who are not, and given the right training and handling they are lovely dogs.
I don't like staffies because although they might have a reputation for being good with children, they have a shocking reputation wrt agression towards other dogs, and I just couldn't be doing with that. But agressive towards other dogs does not equal agressive towards people and so if people choose to keep them that doesn't make them irresponsible.
There is, in fact, a documented case of someone having been killed by a pomeranium (sp?) now that's a sort of dog you could imagine sticking a stick up its arse and using as a feather duster, and most wouldn't consider capable of causing damage beyond a quick nip.
It's never black and white. and ultimately it's like this.
if a child crawls over/pulls/hits/kicks a dog and it bites that child the child is at fault, or the parent for allowing the behavior if the child is too young to know better.
If the dog has been bred for agression and bites then it is the breeder/owner's fault.
If the dog attacks unprovoked and there is no underlying medical reason for this then there is no explanation and one could blame the dog. but tbh unprovoked attacks are so rare as to be almost unheard of. if you delve deeper there is almost always an underlying reason.
The hysteria over dogs is worse than the hysteria over paedophiles.