It applies to all humans to a varying degree.
Social conditioning, both involuntary and voluntary (with a heavy emphasis on voluntary as it has become the dominant social environment with the internet), shape our perceptions of the world.
However, not everyone is effected equally by it. Genetically, not everyone's brain is wired the same and there are differences between political affiliations at a genetic level.
But, that isn't to say people can't look past both inherited and social affects; but it does require a certain type of personality or thought process.
Edit: None of this excuses poor behavior. Unless one has a damaged frontal lobe, there is no reason to not hold people accountable for their beliefs and actions. A belief is one thing, but beliefs spring into actions and some beliefs are objectively incompatible with societal mores; Nazis being the most prominent on the list of objectively wrong.