MARRIAGE MUST DISCRIMINATE
For marriage to have any meaning it must exclude certain types of relationships. In other words it must discriminate.
Many relationship types exist, some are currently more socially approved than others and some are currently illegal. Each of the following are all consensual relationship types which all campaign for marriage equality:
- Same-sex couples
- Polyamorous throuples etc (about 2% of the global population lives in polygamous households and an estimated 50,000 people in the US)
- Platonic related couples (such as sisters)
- Single people in a self-relationship
Unless marriage includes all relationship types then it must discriminate and draw a line, the question is where to draw that line. For millennia, marriage has overwhelmingly been between a man and woman, therefore the burden of proof is heavily on those who argue that marriage can maintain its essential public purpose while increasing the relationship types involved.
From Ben Shapiro:
[S]ame-sex marriage proponents assume that a right to same-sex marriage exists, placing the burden of proof on traditionalists to deny that right. Forcing tradition to shoulder the burden of proof reverses logic. Tradition is the working wisdom of experience. The new should have to overcome the presumptive efficiency, economy and rightfulness of tradition in order to prevail. Change should always have to prove itself-after all, change has never been tried.
This is not to say that tradition should always prevail. Sometimes change will meet its burden of proof: anti-slavery advocates, anti-segregation advocates and anti-sexism advocates made their cases strongly and forcefully, overcoming the weak arguments for tradition. But constant social experimentation-perpetual change justified only by empty assumptions about the infallibility of the New-discards experience in favor of untested theory.
An immature society asks, “Why shouldn’t we?” assuming the past is antiquated. A mature society sees the proven value of the old and the possible value of the new, asking, “Why should we?” Sometimes change should be undertaken; sometimes not. This is only right: Some change is progress, while some change is decay. We can only tell progress from decay by asking change to make its case-to meet its burden of proof.
https://townhall.com/Columnists/benshapiro/2007/07/25/the-most-important-political-trick-in-the-book-n1168959
Similarly, in his dissent (Obergefell vs. Hodges, 2015), Chief Justice Roberts said:
As a result, the Court invalidates the marriage laws of more than half the States and orders the transformation of a social institution that has formed the basis of human society for millennia, for the Kalahari Bushmen and the Han Chinese, the Carthaginians and the Aztecs. Just who do we think we are?
https://www.supremecourt.gov/opinions/14pdf/14-556_3204.pdf