It has become increasingly obvious in the last few centuries, that the world seldom presents a true duality—where there is a single clearly good side and a single clearly bad side to any situation.
The answer to this, multivariate logic (which simply means many variables) has been identified and found very useful by many different problem solvers over the past century, but the techniques have yet to penetrate very deeply into the common person’s sphere.
The tendency is to try and force any problem into terms of one of two possible solutions. Sometimes, this works. Often, it forces people to become blind to alternative solutions which do not require the embrace or discarding of the proposed duality.
Take the case of marriage. The issue, as presented to the public in the media, often is presented as either permitting or denying same-sex unions. The true issue is: are people permitted to make their own decisions as to what spiritual and economic unions they create? If not, what is the basis for prohibiting it? If so, under what conditions do we permit such partnering? Do we, external to such a partnering, indeed, have any right to set conditions?
We have already determined in this society that it is not a good idea to permanent unions involving pre-teens. (Although there are larger societies than ours where this is commonplace.) Our basis for this decision is fuzzy, but boils down to the “lack of capacity” on the part of pre-adults to make such contracts. And, in fact, in societies where such contracts are common, they are seldom executed by the individuals involved, but are in fact agreements upon the part of the respective clan adults on their behalf.
There is an unstated assumption in this argument that a union involves only two persons. Again, there are numerous examples of societies, which permit or encourage unions between multiple persons, including subsets of the prevailing western European mores.
Another assumption is that such unions are “permanent” while this is true in some minority of cases, true monogamy is extremely rare in humans and other mammals. What is practiced commonly in the West is serial polygamy, where people partner, usually in pairs, for periods of months or years, and then dissolve that union and reform a new one with different partners. Often, there is some overlap in partnering.