Well, this is a fine mess.

After years of moaning about various “conspiracies” against them, conservative activists finally have a real (i.e., not manufactured by Fox or inflated by Limbaugh) piece of evidence to take before the court of public opinion.

Meaning, of course, last week’s revelation that the Internal Revenue Service has been giving extra scrutiny to groups with the words “tea party” or “patriot” in their names. Extra scrutiny from the IRS is about as welcome as extra scrutiny from the proctologist, so one can hardly blame conservative groups for complaining, as they’ve done since last year. Unfortunately, those complaints got no traction until Friday, when the IRS admitted the practice. Lois Lerner, director of the IRS division in charge of tax exemption, was speaking at an American Bar Association conference in response to a question about whether the conservative groups had been singled out. She admitted they were.

These groups reportedly amounted to about a quarter of the 300 organizations flagged for review between 2010 and 2012, but according to Lerner, there was no political intent. Rather, she says, the words became a shortcut used by employees to help them sort through the explosion of groups seeking tax exemption under the Internal Revenue Code. The relevant Code section, 501 (c) (4), requires that any exempt group be working to promote “social welfare” and that political action not constitute its “primary activity.” The groups the IRS flagged were not necessarily denied exemption, but were subjected to extensive questioning and required to produce membership lists and donor information.

Tuesday, the Justice Department launched an investigation. Two congressional committees are also looking into the matter. Every taxpayer not employed by the Obama administration should welcome the news.

Under the most charitable interpretation of the facts, this unit of the IRS used god-awful judgment. Under the least charitable, it engaged in ideological harassment inimical to and violative of, the First Amendment.

Taxpayers deserve to know which it is. And how long it has been going on. And whether groups of other ideological stripes have been similarly targeted. And how the malfeasance — assuming it is malfeasance — will be punished. And what safeguards will be put into place to ensure this sort of thing never happens again.

Frankly, Congress needs to address the regulations governing which groups get tax exemption in the first place. The existing standard noted above is porous enough that groups most people would define as political (Crossroads GPS, Priorities USA) are somehow nevertheless declared tax exempt, free to flood campaigns with unlimited money from sources they are not required to disclose.

One could argue, then, that the tea party and patriot groups singled out by the IRS are guilty mainly of playing the same old cynical shell game that has become all too familiar in recent years. But until that game is outlawed, the rules are what the rules are and they must apply evenly, regardless of ideological faith.

Some observers will find the controversial tea party and patriot groups less than sympathetic illustrations of that point. But every group is controversial to somebody;. And only by vigilance toward everyone’s rights do we protect anyone’s rights.

It’s too easy to imagine some future IRS office using different shortcut words (“pro-choice,” let’s say or “Islamic”) to sort through applications for tax exemption. That possibility ought to temper any temptation among tea party foes to be cavalier toward this abridgement of conservatives’ rights. Better they should be thankful nothing like this has happened to them.

Yet.