@Citizen_Justin #83335
Yes, dogs can, all on their own decide one type of human is wrong. Usually, it's lack of socialization.
I had a Akita mix who disliked men and was even worse with Black men. She loved kids. She liked 95≈% of women, no matter the color, but Black men or a guy wearing a black shirt, she needed to be on a leash.
I'm told there are dogs equally suspicious of whites, although I've never encountered one in the wild, so to speak. Plenty of dogs who dislike vets, and a few who disliked me personally, though.