have not read above comments yet, but NO, i do NOT trust my dog's growl to indicate anything other than MY DOG is uncomfortable about something. I do not extrapolate that to mean that person is evil.
My dog used to growl, be unsure about humans with big furry hoods pulled up. this in NO WAY indicates the person wearing the big, furry hood had bad intentions, this in NO WAY indicates my dog has some E.S.P about human personalities, it only indicates, there is 'SOMETHING' about that person, that my dog is uncomfortable/unfamiliar with.
HAHA, once my dog, who is dog-aggressive, barked his head off, at a BABY in the next car over, who had PIGTAIL hairdo and to Buddy, he thought she was a dog in the car to bark at....facepalm!! but, Buddy had never seen a baby with round little pigtails before, it wa kind of dark in their car, so it coulda been a new creature or a dog, near as Buddy could tell. It made for a long stoplight.... I still imagine, that the pigtailed baby had a perfectly lovely disposition, and no malice towards us.
Some dogs react to different things about humans, especially characteristics *they* are unfamiliar with, that we might not even notice, mustaches, sunglasses, limps, size, deep voices, extremly squeaky voices, frown lined faces, thick eyebrows, whatever. Some dogs much prefer women to men, and some dogs especially dislike large or loud talking deep voiced men.
(of course, when i realized that, that hoods frighten Buddy------i set about having people with hoods, especially big furry hoods, give Buddy treats!!! and that was the end of his 'thing' with big furry hoods) Unfortunately, i don't know any lil kids who wear pigtails, so he continues to bark at kids with pigtail hairdos in nearby cars...sigh.
I've also noticed *my* dog is extremely suspicious of unexpected humans we encounter in the dark. Now, if he sees the human approaching, he is on alert, but does not react. But an unexpected, no approach seen human, in the dark, makes him growl.
Even if it a lil sweet old lady, in the dark, if unexpected, my dog might growl at a surprise human right there. Which i have not worked to dissuade him from doing, i like that in him. My dog, btw, is slightly afraid of the dark anyway, and way way likely to be tense, if it is dark outside. It's his thing.
{we can work on this "Fear of The Dark" with him, we can get him calm in the dark, but, if we go too long without working on this issue, he slowly defaults back to his "It's dark outside!! maybe there will be monsters?" attitude...sigh.}