Because the sanctity of religion is at stake...
USAToday has a guest opinion today entitled "Campaigning from the Pulpit: Why Not?" by Richard Garnett, a law professor at Notre Dame. After arguing that the Constitution does not constrain the church from engaging in political activity, Garnett concedes:
True, there is the matter of the tax laws. Churches have, for centuries, for the most part been immune from taxes imposed by secular authority. Accordingly, the United States has long exempted corporations organized and operated exclusively for religious purposes from federal taxation. This exemption, however, comes at a price: Like other tax-exempt charitable organizations, religious communities may not engage in activities and expression that are regarded by government as excessively political (or, perhaps, as insufficiently religious).This sounds nice, doesn't it? We don't want the state censoring the churches - hooray! But this rather easy sentiment misses the point. Unless we want churches to become arms of political parties and campaigns, hiding from election and taxation laws under the banner of religion, demeaning the important pedestal on which we place religious expression in this country, then those difficult lines and labels he references will have to be drawn. And drawn by the state, of course.It is the regulation of the churches' expression, and not their expression itself, that should raise constitutional red flags. Religious institutions are not above the law, but a government that respects the separation of church and state should be extremely wary of telling churches and religious believers whether they are being appropriately "religious" or excessively "political" or partisan. Churches and congregants, not bureaucrats and courts, must define the perimeter of religion's challenges. It should not be for the state to label as electioneering, endorsement, or lobbying what a religious community considers evangelism, worship or witness.
Maintaining that wall protects the sanctity of religion.
You would think, from this piece, that the IRS and FEC have been shutting down churches left and right. Clearly that is not the case--far from it.