The first is simple: An injustice is happening. Yes, the "empathy gap" is apparently a real thing, as much as we may dislike the notion of our deep-suited subconscious racism. But science doesn't contort itself to the likes of well-meaning liberals. Nevertheless, a statistical tendency to have less empathy is not a justification to have no empathy. "Science proves we're racist in our hearts" is not an excuse to act in a racist manner. Unless you're a total sociopath, you should recognize the basic humanity of a murdered black child—or adult—no matter your race.
The second is less selfless/compassionate and more self-centered (the meeting of these two concepts being pretty much the definition of enlightened self-interest).
White people are significantly less endangered by trigger-happy officers (and civilians). The numbers indicate that we’re much less likely to end up dead, even when we're unambiguously breaking the law. But if we allow anyone—including people who don't look exactly as we do—to be slaughtered indiscriminately, we’re saying that we’re okay with it. That we’re okay with a horrific abuse of power existing in the world.
"Less endangered" does not mean "not endangered." "Safer" does not mean "safe." If the cops do it to black people, they can just as easily do it to us. The fact that they generally don't is irrelevant. Oppression does not exist in a vacuum.
Even if you don't care about black people at all—that is, even if you totally suck—you care about yourself, right? You care about your life. Every police officer let off the hook for brutally killing Eric Garner could just as easily kill you if he so chooses.
All of humanity is connected. Remember the words of Pastor Martin Niemöller (1892–1984):
First they came for the Socialists, and I did not speak out—
Because I was not a Socialist.
Then they came for the Trade Unionists, and I did not speak out—
Because I was not a Trade Unionist.
Then they came for the Jews, and I did not speak out—
Because I was not a Jew.
Then they came for me—
and there was no one left to speak for me.
Now try to transcend the empathy gap, for a moment. You’re not an evil monster for your subconscious racist tendencies; but neither must you fall victim to them. That is how we become monsters and victimizers. It’s how we perceive twelve-year-old black boys to be seventeen, and 17-year-old black boys to be threats. Or, more likely, how we forgive officers who do exactly that.
Enough. Let’s hold our police force to a higher standard. They can be better. We can be better. To paraphrase Shakespeare:
Hath not a black man eyes?
Hath not a black man hands, organs, dimensions, senses, affections, passions?
Fed with the same food, hurt with the same weapons, subject to the same diseases, healed by the same means, warmed and cooled by the same winter and summer, as a white man is?
If you prick us, do we not bleed? If you put us in a chokehold, do we not lose breath? If you shoot us, do we not die?
The point resonates: The “other” isn’t so other that his life’s worth is distinct from yours. And the “they” that Pastor Niemöller described is still very much alive. More alive than a certain black teenager, wearing a hoodie and walking in the rain.
They're coming for black people. Speak out. For their sake, for your sake, for humanity entire.