Alas, Lucian Truscott IV is a left wing jerk. Unlike at least one brother that I know, and unlike his father who was a truly great man.
The DNA tests that were performed showed that Sally Hemmings first child was not related to Jefferson, and were unable to show if subsequent children were decendents of Jefferson. Contemporary accounts suggest that subsequent children of Sally Hemmings were likely descended from Randolph Jefferson, Thomas's brother.
In any case, Thomas Jefferson's wife was half sister to Sally Hemmings mother (Mrs. Jefferson and Sally Hemming's common father had a habit of visiting the slave cabins).
So the cousins are just another generation back that what LT IV is telling them. On the other hand, who looks back hundreds of years to find their virtue or blame? That habit belongs more to the English royalty from which we won our independence, rather than the habits of citizens of the republic that we enjoy and safeguard.
People have a right to know their roots.