You need to send documented information.
I think he is basically right. Go easy on him here. Don't ask for documentation; we're only discussing things here, like people sitting down in our living rooms for a social party. It's not an academic seminar. We don't all carry our books around everywhere we go; and we often just remember we saw something about it 1 time. ;-)
From the Library of Congress website: "Slavery in the District of Columbia ended on April 16, 1862, when President Lincoln signed a law that provided for compensation to slave owners. An Emancipation Claims Commission hired a Baltimore slave trader to assess the value of each freed slave, and awarded compensation for 2,989 slaves."
http://www.loc.gov/exhibits/treasures/trm009.html