Comment: Sorry, RCW, but the selective Twitter quote does not demonstrate racism except when taken out if its context, as the author most egregiously does in this case.  The ellipses come from an immediately prior tweet:  "...Such poor leadership ability by the Mayor of San Juan, and others in Puerto Rico, who are not able to get their workers to help.  They...".  The "them" in the quoted tweet is about the Mayor of SJ and her leadership team, not about Puerto Ricans, generally.  Prior to this, his tweet was that Democrats are pressuring the Mayor to tow the party line.  
Perhaps he is racist; he wouldn't be the first president to be so, either Republican or Democrat, but selective quoting like this makes those who make the racist claim look foolish or desperate.