The film I saw was actually rather fair to both Thomas Jefferson and Ms. Hemmings. I guess we will never know the real story.
One thing I didn't know was that Jefferson was actually opposed to slavery. He inherited his slaves from his father, but under the law at that time, he could have been prosecuted if he tried to free his slaves. There are indications he was good to his slaves and his opposition to slavery is documented. He ultimately did free a couple of his slaves during his life and in his will he freed several others upon his death.
These are stories on the official Monticello website, but most have been corroborated by other sources.
Slavery was a terrible institution. Most of the stories about the kind and benevolent slave owners were fabricated by daughters and granddaughters of the Mater who felt guilty and wanted to enjoy some denial. Some, of course, did provide somewhat well by the standards of the day, but when the will was read and the property began to be distributed to the heirs, benevolence went by the wayside.
This was the fundamental problem with ending slavery. Many in the South agreed with the moral argument of the Abolitionists, but they also felt bound by their cultural responsibilities that demanded that the head of the household was responsible to equitibly distribute his wealth to his widow and children. Almost all of them favored their children over their slaves.
Jefferson owned over 700 slaves in his lifetime. Some were inherited from his father, some came from his marriage, some were bought by Jefferson. He freed 10 slaves in his lifetime. Five were freed while he was alive and five were freed in his will after his death. All ten of those slave were members of the Hemming’s family. Within a few months of his death, the slaves at Monticello and the other Jefferson estates were sold to help pay off $100,000 in debts owed by Jefferson.