Two recent news items highlight a troublesome tendency in political discourse to grab whatever allies one can get, without regard to the ultimate damage done to the decision-making process itself.

In England, the House of Bishops of the Church of England earlier this month took an official position against two established political parties, and threatened disciplinary action against any member of the clergy who aligned himself or herself with one of these parties.

The two parties—the British Nationalist Party (BNP) and the National Front—seek restriction on immigration to the UK, and oppose what they claim to be preferential treatment for immigrants over native-born Britons. They also oppose any introduction of sharia law into Britain—a position contrary to that of the immediate past Archbishop of Canterbury, Rowan Williams, who called for “accommodation with some aspects of Muslim law.”

I admit to knowing very little about either party. Much of what I do know I don’t like (aside from the anti-sharia bit). If an individual who happens to earn his living as a paid God expert were to say, “Speaking for myself, and leaving what God does or doesn’t think out of it, I think the BNP is despicable,” I wouldn’t have a problem with that.

That’s not what’s happening here. An official religious organization, acting in its religious capacity—in this case, which happens to be the official religion of the state—is proclaiming that mere membership in a particular political party is against the will of God. As one BNP spokesman asked, “Where is it going to end? Are BNP members going to be allowed to be buried any more in churches?”

“God is on my side” is the single most dangerous, anti-rational argument anyone can make about anything. There’s no answer to it other than “No, he isn’t.” If you think it’s terrible when Pat Robertson or Osama bin Laden says something like that, you’re right. It’s just as terrible when a liberal church does it, even in a cause as honorable as opposition to racism. If George W. Bush had ever said “We do what we do because God is with us,” humanists would have jumped all over him. So why is it ok when his successor utters those words?

The second news item is from North Carolina, where the United Church of Christ and other liberal clergy are challenging that state’s constitutional ban on same-sex marriage, on the grounds that it violates their right to free exercise of religion. They claim they should be able to perform marriages for whatever individuals God tells them they should, and government shouldn’t get in the way of that.

Some advocates of same-sex marriage find delightful irony in the fact that they’ve been fighting organized religion for years, and now along come some different God experts with a novel wrinkle suggesting that religion has actually been on their side all along. “Hoist with his own petard!”

It doesn’t take a psychic, though, to predict what will happen if these plaintiffs should prevail. Quicker than you can say “Latter-Day Saints,” some sects of Mormons and Muslims will be in court, claiming (quite correctly) that their god authorizes polygamy, and it violates their right to the free exercise of their religion for government to get in the way of joining whatever agglomerations God tells them to in legally binding marriage. And they will be right—if there’s a difference between the religious freedom rights of North Carolina liberals and of Utah Mormons or Michigan Muslims, it’s not one I can fathom. Then will come the crackpots claiming a God-given right to marry their siblings, or their children.

The Supreme Court is certainly correct when it calls marriage “the most important relation in life.” It is so important that it needs to be thoughtfully regulated by democratic government, under a consistent and predictable set of rules. Allowing anyone who claims to have a hotline to God to make up rules as he goes along trivializes the whole institution.

We’ve actually fought this one already. The Morrill Act, signed into law by President Lincoln in 1862, banned polygamy in the territories, and it was Utah’s defiance of the Morrill Act and its successors that persuaded Congress to prevent Utah from becoming a state for decades. In 1887, Congress actually passed a statute dis-incorporating the entire LDS church and authorizing the seizure of its property, helping to prompt a revelation from God to the LDS president to back off on polygamy (at least officially).

Marriage is not what some God expert says it is. It’s too important for that. Marriage is what a democratic, responsible government says it is, for all citizens equally. If you don’t like the rules, then try to change them—as same-sex marriage advocates have been doing, with gratifyingly increasing levels of success.

The fight for racial and marriage equality needs to be won the right way, through reason, patience, and the political process—not by anti-rational means that will ultimately create more problems than they solve.