Their intentins go a bit deeper than simply creating doubt. The bally-hoo over the Jefferson/Hemings claims was part of a much broader attempt to stir up old antagonisms within the American mainstream--on a North/South basis--and undermine all potential rallying points. (See Creating Hate In America Today for more on the subject of this thread, in the greater context of trying to undermine the Southern traditions, as part of that onslaught.)
The sad truth is that there are those who will seek to exploit every opportunity to undermine the cultural heritage and self-respect of the American mainstream. There are signs of a renewal of traditional values in some areas, in response to the recent Terrorist attacks. Now is a good time to launch an ideological counter-attack.
William Flax Return Of The Gods Web Site
Maybe not, after all Sally's children were the only slaves freed upon his death.
However, Jefferson was as duplicitous a man as ever occupied the White House. He was also one of the most hypocritical and, with the exception of stumbling into the Lousiana Purchase through blind luck, accomplished little of benefit to the U.S. when president. Like Clinton he had no effective opposition and a loyal claque of news media outlets to tout his claimed virtues and attack his enemies with calumnies and falsehoods so he was re-elected.