The basic assumption that people like Daniel seem to argue from (and for) is that because black Americans were once enslaved and horrifically abused as a class of humans, the abuse by a black person of anyone from the historical abuser class (whites) is nothing to get worked up about because it simply doesn't register on the scale of harm. They really seem to not see nor to care about equal treatment as an ideal and principle, but rather define equal justice as a balancing of the harm scale: if millions of black people suffered unjustly at the hands of white people, then it's no big deal—practically karma!—for a white person to suffer unjustly at the hands of a black person. They dismiss it as a problem because they think of injustice as a ledger and they are tallying the incidents and failing to see enough harm registering on the white side to warrant concern. It's a profoundly retributive worldview, which seems to be a consequence of a cultivated victimhood mindset.