Subconscious vs. Conscious Racism
The initial question we need to be asking ourselves is this: why do cops so often get "jumpy" with their weapons around black people?
The answer is subconscious racism. Chances are, in most of the cases we hear about, the police officer involved did not wake up in the morning, look in the mirror, and ponder ways that he could harm another race or ethnicity. Racism exists--absolutely--but the amount of pure, hate-driven, violent racists in this country is negligible in the grand scheme of things, especially when compared to the general murder rate. The problem here resides in a different kind of racism.
As a Harvard study has proven, almost everyone--including black people--have a subconscious bias against the black community. While one may be consciously impartial to any race or ethnicity, most of our brains believe otherwise. This discrepancy between what we "know" and what our brains may "believe" doesn't stop at how we perceive each other; it also determines how we see objects. You're more likely to be killed by a deer than you are to be eaten by a shark, yet we panic when we see sharks and readily approach deer without a care. This is because movies like "Jaws" and rating-driven material like "Shark Week" are readily available in our subconscious memory bank while--unfortunately--no major movies or television marathons have been made about killer deer.
What's scary about the subconscious is that no amount of formal education can alter it. You may be well aware that only five people per year are killed by sharks, but most of us will scream our way back to shore at the sight of a fin in the water. The only way to alter the subconscious is through immense exposure therapy (or surgery, in drastic cases). If you live amongst the sharks for a few hours, you might overcome your fears. The problem is that--once you leave those waters--your fear will likely return upon another visit. Only after several sessions may that nervous feeling entirely subside, and that's assuming you're never actually attacked. If you're attacked, it's back to square one.