There are people who are generally afraid of dogs, usually because of being attacked when very young as I was. I have no problem with most dogs as soon as I can get to know them. I like dogs. I have a dog that is a member of the family.

There are some dogs who respond aggressively to smelling fear on a person. We call them "fear biters". These dogs can be perfectly sweet with everyone else. If you have a fear biter, it is your responsibility to keep it away from people who fear unknown and/or aggressive-acting dogs. With a fear biter, no amount of getting to know the dog works. They remain violent, probably in a feedback loop with the person who experiences increased fear because of the dog's behavior.

One of the unpleasant parts of this is the number of people who assume that the dog's reaction to the dog-fearing person means there is something untrustworthy in the person.