Read the whole thing. It is the smoking gun.
According to the White House Visitors Log, provided here in searchable form by U.S. News and World Report, the president of the anti-Tea Party National Treasury Employees Union, Colleen Kelley, visited the White House at 12:30pm that Wednesday noon time of March 31st...
April 1-2, 2010: The new Acting Manager, Technical Unit, suggested the need for a Sensitive Case Report on the Tea Party cases. The Determinations Unit Program Manager Agreed.
In short: the very day after the president of the quite publicly anti-Tea Party labor union -- the union for IRS employees -- met with President Obama, the manager of the IRS "Determinations Unit Program agreed" to open a "Sensitive Case report on the Tea party cases." As stated by the IG report.