To call racism the sin of indifference is to minimize racism.  

If you've "never openly (or inwardly) disliked black people or said anything disrespectful of them," and "always had at least one black friend," the only thing that could explain your feeling like a racist today --- do you really?  Or are you just "virtue signaling"? --- is irrational white guilt, which has been put there for a political reason.  This is not to say that indifference is not sinful.  It's ridiculous to call it racism unless you are indifferent to blacks because they're black.  Go do some community work for those to whom you've been indifferent, not a racist.