When a discussion site - in this case DU - caters to and nurtures the victimology of PC minority groups*, it attracts members of those groups who most define themselves by their victimhood, and are acutely sensitive to victimizing acts, however minute. Just as nurturing hatred toward those with whom they disagree inevitably would turn inward, as it has with CHILL vs. Bern, it was inevitable that members of PC minority groups' victim hypersensitivities would be turned inward, resulting in wranglings and recriminations, and those PC minority victims leaving in search of a safer safe place. Consequently, DU is largely a Bizarro-World of lots of white people who are down with blacks' victimology, but few actual blacks.
* PC minority groups, e.g.: blacks and Hispanics are PC but East & Southeast Asians, Indians, and Jews are not; Muslims are PC, but religious Jews are not; atheists are PC, but Evangelical or Catholic Christians are not.