Unless there is something we don't know about Shirley Sherrod's job performance, it is safe to say, based on what we now know, that Secretary of Agriculture Tom Vilsack acted on the basis of provisional information that drew him to make a false conclusion about her views and what point she was trying to make. It was a good faith mistake based on the bad faith of others.
The White House doesn't like to intervene when racial politics bubble up, except for the times it does -- like when a black Harvard professor that President Obama knew was involved in a fracas with a white Cambridge police officer. Some of President Obama's friends have had a nagging suspicion that racial discourse in the country is coarser than it was when he took office because, perhaps, people hadn't felt the need to express themselves as honestly as they do now, with a black president in office, with the country having elected a black president to office.
The executive branch realizes that the White House is extremely sensitive to the charge that Obama is using his presidency to advance the cause of black people. It's a tremendously silly charge, and maybe the White House shouldn't be so sensitive to it, but it's a real sensibility. One suspects that the moment that the specter of reverse racism was raised, the USDA's political appointees reacted almost unconsciously because they assumed the White House would blanch when the videotape was played.