The Democratic Party has undertaken an ostentatious outreach to religious voters, creating a Faith Advisory Council and cultivating clergy around the country. But these efforts might be more credible if Democrats were not simultaneously trying to incite conflict between Roman Catholics and Protestants in Louisiana — and managing to offend both groups in the process. According to a recent television ad run by the Louisiana Democratic Party, the leading Republican candidate for governor, Bobby Jindal, has “insulted thousands of Louisiana Protestants” by describing their beliefs as “scandalous, depraved, selfish and heretical.” Mr. Jindal, the attack goes on, “doubts the morals and questions the beliefs of Baptists, Methodists, Episcopalians, Pentecostals and other Protestant religions.” The ad is theologically ignorant — Methodism and the others are not “religions,” they are denominations. The main problem, however, is that the ad stretches the truth so filo-thin it can only be called a smear. Mr. Jindal — a convert to Christianity from a Hindu background — has none of the politician’s typical reticence on religion. “I’m proud of my faith,” he told me in a phone interview. “I believe in God, that Jesus died and rose. I can’t divide my public and private conscience. I can’t stop being a Christian, and wouldn’t want to for a moment of the day.”

And Jindal’s chosen tradition is a muscular Roman Catholicism. In an article published in the 1990s, he argued, “The same Catholic Church which infallibly determined the canon of the Bible must be trusted to interpret her handiwork; the alternative is to trust individual Christians, burdened with, as Calvin termed it, their ‘utterly depraved’ minds, to overcome their tendency to rationalize, their selfish desires, and other effects of original sin.”

And elsewhere: “The choice is between Catholicism’s authoritative Magisterium and subjective interpretation which leads to anarchy and heresy.”

This is the whole basis for the Democratic attack — that Mr. Jindal holds an orthodox view of his own faith and rejects the Protestant Reformation.

He has asserted, in short, that Roman Catholicism is correct — and that other religious traditions, by implication, are prone to error. This is presumably the main reason to convert to Catholicism; because it most closely approximates the truth. And speaking for a moment as a Protestant: How does it insult us that Roman Catholics believe in … Roman Catholicism? We had gathered that much. This Democratic ad is not merely a tin-eared political blunder, it reveals a secular, liberal attitude: that strong religious beliefs are themselves a kind of scandal; that a vigorous defense of Roman Catholicism is somehow a gaffe.

This is a strange, distorted view of pluralism, which once meant civility, respect, and common enterprise among people with strongly held and differing convictions.

In the liberal view, pluralism means a public square purged of intolerance — defined as the belief in exclusive truth-claims and absolute right and wrong. And this view of pluralism can easily become oppressive, as the “intolerant” are expected to be silent.

On the receiving end of those expectations, Mr. Jindal has given these issues considerable thought. “This would be a poorer society,” he told me, “if pluralism meant the least common denominator, if we couldn’t hold a passionate, well-articulated belief system. If you enforce a liberalism devoid of content, you end up with the very violations of freedom you were trying to prevent in the first place.” On the evidence of the Louisiana ad, Democrats have learned little about the religious and political trends of the last few decades.

For all its faults, the religious right built strong ties between conservative Catholics and conservative Protestants on issues such as abortion and family values, after centuries of mutual suspicion.

Evangelicals gained a deep affection for Pope John Paul II, and respect for Catholic conservatives such as Justice Scalia. And conservative Protestants recognize that secularist attacks on Catholic convictions are really attacks on all religious convictions, and could easily be turned their way.

“The most passionate defenders of my beliefs,” says Mr. Jindal, “have come from people who don’t share my beliefs.” In one news account, the pastor of the First Baptist Church of New Orleans gave this reaction to Mr. Jindal’s writings: “Anybody who reads this whole article and ends up angry just needs to grow up.” That is a good definition of genuine pluralism — an adult respect for the strong convictions of others.

“Bigotry,” said Catholic writer G.K. Chesterton, “may be roughly defined as the anger of men who have no opinions … the appalling frenzy of the indifferent.” And religious bigotry is offensive everywhere, including on the bayou.