Letter to NPR Ombudsperson. Contact her here: http://help.npr.org/ics/support/default.asp?deptID=5670&task=ticket
It was unbalanced of NPR to "rebut" Howard ZInn's legacy without doing the same for other controversial figures on the right.
Horowitz's statements don't reflect the balanced conscience of a conservative or the measured estimate of a historian. He is a media showman and NPR bought his snake oil.
You ruined your segment with his commentary, and you further confirmed the sense that some of us have that you are interested only in "fake balance" and not news or commentary based on merit.
Read the FAIR account, here: http://www.fair.org/index.php?page=4009