There is no evidence that a person is a threat to that dog. But the dog believes that a threat is real.
Maybe it's because this dog is conditioned this way, maybe this reaction is in its genes, maybe it doesn't really have a choice.
But it's almost always different with people. We have a choice. A choice of scolding somebody or a choice of letting go.
Animalistic reaction is always ignited when we are not sure what to do next, when we live by somebody else's agenda.
Otherwise, when an artist is on a mission, her reaction is: "do not engage because the threat isn't real."