AN ARGUMENT AGAINST POLYAMOROUS MARRIAGE
P1. Polyamorous marriage must appeal to an understanding of marriage which equally applies to other relationship types
P2. Over time, any arbitrary exclusions of relationship types in marriage will disappear
C. Therefore polyamorous marriage will lead to other relationship types being included in marriage
Slippery slopes are often dismissed out of hand however Eugene Volokh highlights some relevant examples related to same-sex marriage.
In Griswold v. Connecticut (1965), the Supreme Court struck down a ban on the use of contraceptives. Griswold deeply relies on the rights of a married couple; nothing in it asserts a broader sexual autonomy right….Yet only seven years after Griswold, in Eisenstadt v. Baird, the Court relied on Griswold to hold that unmarried couples have a right to use contraceptives.
The following year, the Court used Griswold and Baird as the foundations for recognizing a right to abortion…And in the recent Lawrence v. Texas, the Court used Griswold as “the most pertinent beginning point” for its decision to strike down laws banning homosexual conduct.https://www2.law.ucla.edu/volokh/marriage.pdf
From the 1960s on, many states decriminalized same-sex sexual conduct…When such liberalizations were proposed, some people warned that these laws were steps down a slippery slope to broader rejection of traditional sexual rules, including towards same-sex marriage. These slippery-slope arguments were dismissed, sometimes contemptuously. The claim that a hate crime law “would lead to acceptance of gay marriages” was called “arrant nonsense.”A proposed antidiscrimination law, people were assured, does not “put Massachusetts on a ‘slippery slope’ toward” “legaliz[ing] ‘gay marriage’ or confer[ring] any right on homosexual, lesbian or unmarried heterosexual couples to ‘domestic benefits.’” “Those that truly have a problem with homosexuality will see [a domestic partnership proposal] as part of the ‘slippery slope’ toward gay marriages . . . . But, this legislation needs to be looked at on the face value of what it is, and it really does very little.” Yet when the Massachusetts Supreme Judicial Court held that the state constitution requires the legislature to recognize same-sex marriages, part of its reasoning rested on the legislature’s decision to ban sexual orientation discrimination: This decision, the Court reasoned, undermined the asserted government interest in condemning homosexuality as immoral, and thus helped strip away any rational basis the law might have had. Likewise, when the Vermont Supreme Court held that the state constitution requires the legislature to recognize same-sex civil unions (marriages in all but name), a large part of its argument rested precisely on the legislature’s past enactment of various gay rights laws, including the enactment of antidiscrimination laws and hate-crime laws that refer to sexual orientation.https://www2.law.ucla.edu/volokh/marriage.pdf
Similarly, when the Equal Rights Amendment was being debated in the 1970s and 1980s (both at the state and federal levels), and the ERA’s foes argued that the sex discrimination ban might lead to legalization of same-sex marriage, such arguments were derided as “emotional scare tactics,” “hysterical,” and “canards.” Yet both the Hawaii Supreme Court and the necessary fourth vote on the Massachusetts Supreme Judicial Court relied on the state Equal Rights Amendments in concluding that the opposite-sexes-only marriage rule was indeed sex discrimination.https://www2.law.ucla.edu/volokh/marriage.pdf