Aside from his frequent racist comments, Trump has operated his real estate in a racist way, excluding dark-skinned rent applicants with a ledger notation, "C" (for colored) that became a permanent record, still existing today.  This is from a report by the Dept of Justice.
http://www.thedailybeast.com/articles/2015/12/15/doj-trump-s-early-businesses-blocked-blacks.html