You have to take context into consideration. I think it is clear the OP used "dindu" as a racial slur.
It's being used as a racial slur, because it is a racial slur, and nothing more. The usage is correct, in context.
It's short for "dindu nuffin". In short, white supremacists insist, regardless evidence, that any black person harmed by a cop or vigilante must be guilty of something.
looking into things, there's the mangled version of AAVE . "Dindu Nuffin" as a mutation of "didn't do nothing" or "didn't do anything". As in, "I didn't do anything", which seems like a reasonable protestation when being arrested or attacked by police without cause.
Also note the hideous, ignorant version of AAVE.
More importantly, there's the assumption that any random black person must be guilty of some serious crime, and therefore must be a "worthy" victim of violence. If "I dindu nuffin" is false, then the person must have done something. And thus, they must have earned being beaten or shot - not due to racism, but rather because black people are somehow incapable of living among the civilized folks. They must fail - not because of any pressure, butbecause they're "dindus".
...I should think this one out a bit more. It's a slur as obvious as "coon" or the dreaded "n-word", but it's a bit new.