It's natural to try and coax "good guys" and "bad guys" out of a narrative, even if by doing so one distorts the truth. History devoid of narrative and this structure (good/bad dichotomy) doesn't fly well with a public spoon-fed on happy endings and absolutes of virtue and evil.
It also doesn't help that history is usually written by older people nostalgic for a time when things seemed less complicated, when they enjoyed the promise of greater opportunity and a far more vigorous and robust health. My grandmothers were endlessly mythologizing their personal histories with obvious and self-evident blind spots to the greater injustices all around them: in fact, they felt entirely justified when confronted with their (occasionally appalling) prejudices.