Warren had a good zinger on gay marriage. It was bad politics.

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WASHINGTON -- Elizabeth Warren had a good line, a zinger, deftly delivered.

How would she respond, Warren was asked at CNN's forum on LGBTQ issues, to a voter who told her, "I'm old-fashioned, and my faith teaches me that marriage is between one man and one woman"?

The Massachusetts senator and Democratic presidential candidate couldn't resist the opportunity for a double dig. "Well, I'm going to assume it's a guy who said that," she began, giving the audience the chance to snicker along about the evident cluelessness of the male gender. "And I'm going to say, 'Then just marry one woman -- I'm cool with that.'"

Warren shrugged, as if to say, no biggie, live and let live. The audience whooped with delight. Warren shrugged again. Then she went in for the easy kill. "Assuming," she said, "you can find one." She turned, clapped along with the audience, nodded in evident satisfaction, put palms up as if to say, what is wrong with people who just don't get it?

It is tempting to ask: What is wrong with Elizabeth Warren? This was a satisfying moment, an undoubted crowd-pleaser that, as the Warren campaign exulted, had generated more than 12 million views on Twitter by the following afternoon. But it was a mistake that evoked missteps of Democratic campaigns past -- a dismissiveness that Warren and her fellow candidates would do well to avoid.

This is bad politics, which may be the strongest immediate argument for shifting course, yet it is something worse than that. It reflects an attitude of intolerance and disrespect toward people of faith. Those who reasonably expect tolerance and respect should think about the importance of practicing what they preach.

On the issue of equal rights for LGBTQ Americans, the country has been on an exhilarating journey of understanding and acceptance, one that reflects the best of the national charter and, more important, the national character. As a legal matter, we have progressed from a Supreme Court that in 1986 declared that it did not offend the Constitution to prosecute two men for having sex in private to a court that in 2015 found that the same Constitution in fact guaranteed the right to same-sex marriage. The court was correct the second time around.

More gratifying, the country has not resisted this legal transformation -- it has embraced it. Dissenting in the marriage equality case, Chief Justice John Roberts warned of a backlash. "Stealing this issue from the people," he wrote, "will for many cast a cloud over same-sex marriage, making a dramatic social change that much more difficult to accept." That was incorrect. A solid majority of Americans -- 61%, according to the Pew Research Center -- support the freedom to marry, including close to half -- 44% -- of Republicans. To the extent there is opposition, it is, literally, dying off: 74% of millennials favor same-sex marriage.

But, but, but. Major religions, including the Catholic Church, continue to teach that homosexual conduct is immoral and to oppose same-sex marriage. That is their right -- their constitutionally protected right. Thankfully, we live in a country that both guarantees the right to marry the person you love -- and protects your right to be wrong about whether that marriage should be permitted. In the years ahead, the country and the courts face the difficult task of sorting through how to balance those competing imperatives.

As that enterprise proceeds, it is important that it be conducted with the respect that Warren failed to display.

Most immediately, this dismissive attitude is politically dangerous. In the short term, Warren's seeming intolerance toward those whose faith rejects same-sex marriage could hurt her with African American voters. In the general election, her comments carried unsettling echoes of Democratic missteps past: Barack Obama on dispirited working-class voters who "cling to guns or religion"; Hillary Clinton lumping Trump supporters into a "basket of deplorables." Intolerant condescension is rarely a winning political strategy.

It's also just bad behavior. Disagree, vehemently; don't disrespect. Tell the imaginary questioner -- and the millions of Americans who share his conviction -- that you believe his view is misguided, intolerant, insulting. Explain why. Don't denigrate his faith, or suggest that following it makes him a loser.

"My faith animates all that I do," Warren, a former Sunday school teacher, said earlier this year. I believe that, which means I believe that Warren, when she thinks it over, will do a better job of respecting those whose faith animates them in a different direction. Jesus loves all the children of the world, as she sang at the CNN forum. Even the ones who are wrong.

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Ruth Marcus' email address is ruthmarcus@washpost.com.