The best and angriest report on the IRS's admission that it investigated Tea Party groups above and beyond its purview comes from Kevin Williamson. His most powerful argument is simply a recitation of what was demanded from the targets.
Those tea-party organizations were sent letters of inquiry demanding information that would seldom if ever be demanded of any other applicant in the process. The IRS demanded lists of donors, names of spouses and family members, detailed information about political views and associations — all of that “under penalties of perjury.” Many applicants dropped out of the process. The questions were remarkably invasive: For example, the IRS demanded to know not only whether political candidates participated in public forums conducted by the groups, but which issues were discussed, along with copies of any literature distributed at the forum and material published on websites. (The IRS has been less forthcoming with its own materials related to this investigation.) If the organizations collected dues, the IRS demanded to know how much they were. It demanded everything down to the résumés of employees. The inquiry was not limited to members of the organization, its executives, or its directors, but included even their family members: The IRS demanded to know — again, under penalty of perjury — whether any of their family members might be thinking about running for office. Its demand for the names of all donors — and all recipients of grants — is in violation of IRS policy.
Why were they doing this? The IRS has already mea-culpa'd, in the sort of self-parodying way that suggests they need more experiece with damage control. ("Mistakes were made"! Who still says that?) Republicans, starting with Eric Cantor in the House, have pledged to hold investigations on why the IRS did this. But if they had a defensible reason (big "if") it was probably a combination of two worries. One: Tea Party groups flowered quickly, and in situations like that you want to see where the money went. Two: As Ezra Klein explains, the rules governing nonprofits are increasingly ill-suited to the reality of nonprofits. The secrecy accorded to 501(c)4s has made them incredibly attractive for people who want to stack money away without having to disclose their donors. Battling this is a big goal on the left right now—the Sunlight Foundation, for example, is obsessed with it. That campaign loses much of its oomph if the IRS becomes scared of asking political groups to prove that they should be free from taxes.