But the argument is specious. If we look at it from the viewpoint of the family, anti-miscegenation is based on ideas of preserving racial purity and maintaining racial supremacy in a region.
The viewpoint of what family? That idea of 'family' is itself a term that religions - Christianity in particular - have coopted to fit their particular restriction and definition.
Its motivation is bad.
That's your subjective opinion; it has exactly as much weight as my judgement that opposition to extending marriage to gay people comes from bad motivation.
Opposition to gay marriage is based on connecting a child to his/her biological parents.
You know how reproduction works, right? If gay people get married, there are no children, that's why so many anti-gay arguments have that specious 'but they can't have children' argument.
It fundamentally supports the offspring of a man and a woman, thus its motivation is good.
That expectation that marriage will produce offspring is a different argument to connecting children to their parents; it's also expressly part of most Christian conceptions of marriage, but there's nothing intrinsic to the concept of marriage. We don't deny marriage to straight people with no intention or capability of having children, so whilst it might be seen as desirable in some parts of the community it's far from a deal-breaker.
It's not the opponents of gay marriage who should be likened to the opponents of mixed race marriage, but those who support gay marriage, because they advocate sterility and prevention of the natural conception and rearing (by both biological parents) of children.
No, they don't, they realise that some people don't want children, some people do, some people on both sides of that are gay, but despite those combinations it turns out that marriage is about commitment to each other and building stable homes that benefit society and culture as a whole, regardless of whether there are children in that household.
As it is, developments in technology and institutions like adoption are increasingly bringing the option of parenting to gay couples.
O.