In the Rocky Mountain News a couple of years ago, Jean Torkelson wrote about comments made by Colorado Springs Bishop Michael Sheridan:
[C]ivil authorities "should consider it a sacred duty" to acknowledge man-woman marriage and protect it against the movement to legalize same-sex unions, Sheridan writes in his monthly column, which appears today in The Catholic Herald. "If marriage means only what any given person says it means, it means nothing," Sheridan writes. "This opens the door to polygamy and any number of other perversions . . . there will be no turning back."
Sheridan writes that marriage is not "a whim of man," but a matter of natural law - that is, inherent in human nature. "God himself is the author of marriage," he said. "What has been understood and accepted - albeit not always lived perfectly - as the exclusive lifetime union of one man and one woman in a covenant of love for the procreation and rearing of children is now coming to be understood in some quarters as the union of any two people for any purpose for any amount of time," Sheridan writes. ... As Catholics and citizens, Sheridan urges, "we must, each of us, do all we can to promote marriage and family life in our society."
Even if God exists, God is not the author of civil marriage in society. Notice how Sheridan wants to define marriage as “the exclusive lifetime union of one man and one woman ... for the procreation and rearing of children.” In our society, marriages don’t have to be for a lifetime and they don’t have to produce children. That’s a fact and it's undeniable. Religious conservatives who argue otherwise are being willfully ignorant and deceitful in the pursuit of an authoritarian, repressive political agenda.
Perhaps Sheridan would advocate laws that would change the current situation in which civil marriage is not bound by his religious beliefs; if so, he is dishonest for not admitting this up front. Currently, though, civil marriage isn’t defined by his religious beliefs and it's doubtful that many people would support any change in that. Nor should they. Marriage is not solely a religious or theological institution and Sheridan does all Catholics a grave disservice by not recognizing this (or, even worse, by pretending it doesn’t exist).
Sheridan has a right to help define what marriage means within the Catholic Church. People have a right to voluntarily submit to Catholic definitions of marriage if that is what they wish. Sheridan also has a right to advocate for changes in the definition of marriage through the rest of society, though he should do so honestly and openly. Sheridan does not, however, have the right to insist that everyone’s marriage be defined according to his theological beliefs.