Even the very language used in the debate is slippery, with homosexuality often described as a "sexual preference." But everyone has sexual preferences. A partner of the same sex is a sexual preference; so is black lingerie. Yet (to the best of my knowledge), homosexuals are uniquely expected to have their whole lives and worldview defined by that sexual preference. There are no black lingerie neighborhoods (alas) or High Heeled Boots Political Action Committees; Democrat Party leaders do not accuse GOP candidates of deep-seated red-lipstick-ophobia. (Well, not yet, anyway.)
The fight over gay marriage in our political realm is not actually about gay marriage, of course. Gays and lesbians will continue to hold ceremonies and cohabitate and call each other "husband" and "wife" no matter what the law says. The question is over a piece of paper, a government document that is usually a minor detail in the process of heterosexual marriages. For every gay or lesbian who angrily accuses the opposition of denying their right to get married, it is worth remembering that a marriage is not a document.
Perhaps the gay marriage issue needs to be discussed in new ways. Proponents could appeal to fiscal conservatives, "Let's subject gays and lesbians to the same IRS marriage penalty you've been enduring for years." Opponents could remind homosexuals of the full picture of modern marriage: "Do gays and lesbians really want to suffer the pain, grief and expense that comes from messy divorces? Doesn't the current law give you a handy excuse to dodge your mother's question of when you'll get married?"