Watching "A Slavery By Another Name" (PBS) was an eye-opener.
Over my life, I've definitely harbored some vague sense that black people are more prone to criminality.
Before you scream at me - let me explain.
I'm saying this was sort of a background association that, as far as I could tell, bloomed in my brain due to cultural influences - movies, family discussions, public discussions. Of course, upon inspection, it would always be easy for me to use my frontal lobes and dismiss this association as silly, and tell myself - with rational thought - that I didn't actually believe that. But it was still there, just suppressed.
This PBS documentary revealed the convict lease system that flourished post civil-war reconstruction. Small town governments passed bogus loitering laws which the police used to arrest black people and put them into the prison population. There, they were leased out as unpaid labor. This was made possible by the exception clause in the 13th amendment, and a retreat by the federal government.
As a result, by the 1940s, there was an alarmingly high number of black people in prisons. That was the birth (or perhaps solidification) of the idea that black people are more prone to criminality. Historians noted that if you went back to pre-civil war days, and looked at how white people regarded black people, you'd read words like 'hard working', 'honest', even 'loyal' (IIRC). The convict lease system totally changed perceptions, and we're STILL living with these skewed and racist perceptions today. Even me - a person born WAY after convict lease ended. A person who, outside of messaging from popular culture, has never had a reason to think any differently of black people.
It seems that echoes of past injustices and conflicts fade slowly. In my opinion, many go through periods of amplification.* I wonder - how many people who are honest enough to recognize in themselves any latent racism, know from where it came?
*The other past conflict that I believe is having amplified effects today: cold war anti-communism efforts. Our government consciously pushed nationalism, patriotism, the supremacy of the individual, and religion - all in an effort to fight communism. We aided rebels, supported assassination attempts, and ousted democratically elected leaders in sovereign nations, all due to our fear of communism. The results are still with us: my extended family is so vehemently anti-communist/ anti-socialist that many sop up the rhetoric from bogus think tanks. They HATE "liberals". They think environmentalists are secret commies. I don't think they'd be so easily influenced by this messaging if they hadn't lived through the cold war propaganda. But this is off topic - just another example of the vestiges of past policy echoing loudly today. (IMO).