Members of the Fundamentalist Church of Jesus Christ of Latter Day Saints at the Yearning for Zion Ranch in Texas can be forgiven for thinking they are being punished for making just another "lifestyle choice."

The compound of the polygamous sect -- a breakaway from the Mormon Church, which long ago forswore plural marriage a century ago -- was raided by Texas authorities, who took more than 400 children from their parents. The group's family tree is so opaque that DNA tests are under way to determine which children belong to whom.

"It's just like in any society in America," one woman at the ranch told a reporter, by way of explaining the confusion over the children. "A mother might have been in two or three relationships, and a child may be confused about what name to give."

There's some truth underneath that self-justification. Family relationships in America have become broken and convoluted -- although nothing on the order of the bizarre sect led by Warren Jeffs, now serving time for forcing a 14-year-old girl to marry her 19-year-old cousin. But with so many people divorced or having children out of wedlock, it's easier to elide questions of family structure and focus on child abuse.

That's the grounds on which the state of Texas moved on the FLDS ranch and confiscated all the children. The problem is that Texas authorities admit that the children were well cared for. The young children and the boys were in no danger. It's only the teenage girls who needed rescuing. That's because it's not child abuse that is the sin of the FLDS, but polygamy.

A polygamous society is inevitably going to tend toward the abuses of Yearning for Zion Ranch. This is why even if Texas went too far and probably will have to give most of the kids back, it acted out of the right motives. Polygamy is fundamentally inconsistent with our values as a society, and people shouldn't be able to maintain islands of it in violation of U.S. laws.

The dynamic of polygamy is that older, higher-status men take as many women as they can. They work to crowd out young men and to make young women as pliable as possible, so as to eliminate any competition from the former and inhibit any tendency on the part of the latter to fall for men their own age. It inherently features brutish sexual competition among men (the winners get many wives, the losers none) and the subjugation of women who are made to serve a man not, in turn, fully devoted to her.

This is exactly how FLDS works. It looks for any excuse to kick out teenage boys. These "lost boys" are left to fend for themselves on the streets. Meanwhile, teenage girls are taught obedience, which can mean, as 13-year-olds, marrying men old enough to be their grandfathers.

With its emphasis on hierarchy and the degrading of individual choice, polygamy is traditionally associated with authoritarian cultures. Jonathan Rauch of the National Journal writes, "No polygamous society has ever been a true liberal democracy, in anything like the modern sense." In his classic book "Men and Marriage," George Gilder argues, "Monogamy is egalitarianism in the realm of love." It promises one woman per man, and limits the ability of powerful men to dominate.

One disapproving columnist says of the Texas raid: "There is a whiff of cultural imperialism here. This is about further marginalizing an already-marginalized way of life." Indeed it is. There are limits to pluralism. In the 19th century, when the Mormon Church still supported polygamy, the U.S. government harried it mercilessly. As Stanley Kurtz points out, the campaign against polygamy related to the effort to democratize Utah.

Now, polygamists are trying to ride on the liberal wave of nonjudgmentalism and of hostility to traditional marriage. Who are we to say what marriage is? As liberal democrats, we've said it before, and have to again.