Paradigms for right and wrong love

  I find it amusing that opponents of same-sex marriage will often put up some kind of slippery-slope argument against it saying that if we broaden our definition of marriage, surely even broader definitions, including things like polygamy and marriages to children, will follow.  I find this amusing, because a great deal of these people support using the bible as a guide to what kind of marriages we should have, and the bible is pretty pro-polygamy, and pretty lax on the whole adult-child relationship thing, too.  Marriage as a system of ownership is also a pretty common theme in the bible.
  There have been plenty of articles written on how the bible is a poor standard for what kinds of marriage should be allowed, but has anyone ever taken a look at other standards, not just for marriage but for what divides "right love" and "wrong love" in general?
  Probably the most common description for what makes right love (or at least marriage) is the "one man and one woman" paradigm.  This has the downfall of allowing things like marriage as a system of person-ownership.  I shouldn't really call this a paradigm either, because it's more of a laundry list of qualifications than an idea about being wrong or right.  I mean, there's no inherent morality surrounding the idea of there a single man, or about there being a single woman.  This idea looks less like a paradigm for right love and more like the shortest way to describe marriage that doesn't include the three most obvious kinds that society finds unpalatable (same-sex, polygamous, and child marriages).
  Of course, I should point out that support for one of the three kinds mentioned above doesn't necessitate support for the others.  When people believe that acceptance of same-sex marriage will lead to acceptance of polygamy or pedophilia, they seem to generally run on the assumption that proponents of same-sex marriage support an "anything goes" standard.  From my experience they're mostly wrong in that assumption, which is good because otherwise we would see widespread support for forced marriages, polygamy, and child marriages.
  A standard that I think is much more common in the pro-gay-marriage camp is the "two consenting adults" (or, less commonly, the "two or more consenting adults") standard.  This one is pretty good, but it has the same problem as the "one man and one woman idea" in that it' not really a paradigm so much as a list of qualifications.  It also has the problem of allowing for marriage-as-ownership and similar scenarios, as long as both parties say they agree to it.  Really, aside from allowing same-sex marriages, this set of qualifications is almost the same as the "one man plus one woman" set.  I want you to think about that for a second, because it really highlights how these both fail as paradigms.  One of them allows a type of marriage that the other doesn't, but neither of them really includes any justification for why they fall on the side they do.
   Now, you know I wouldn't bring up this subject unless I had my own paradigm to proscribe, and I do.  It can be described in one word: equality.  For any relationship or marriage to be right, good, and healthy, it must be equal.  The equality paradigm would exclude polygamous relationships, because they carry in their composition the implication that a man is worth 4 (or however many) women, while a woman is worth 1/4th of a man.  The equality paradigm would also exclude pedophilic relationships, because an adult is at a fundamentally higher position in society than a child.  It would also exclude bestial relationships, because a human has a much higher position in society than an animal.  This applies to more than just the members of the relationship but also how they act towards each other; any relationship where one person acts as the ultimate decision-maker is unequal.  Forced, coerced, and ownership-based relationships would also be excluded, for obvious reasons.
    What this paradigm would not exclude are opposite-sex relationships or same-sex relationships.  Nor would it exclude couples who like to engage in S&M, assuming that what they do is decided based on the mutual enjoyment and consent of both parties.
    Now why is this the best paradigm, you ask?  Aside from not including the negative kinds of relationships that I mentioned the above paradigms imply, it's also based on a pretty good ideal that a lot of people seem to be quite fond of.  When you love someone in a romantic way, you put them on equal importance as yourself and you become partners.  "Partners" in relationships means the same thing that it does in business; they don't become your boss and they don't become your subordinate.  They become your partner - your equal - and treating them like your equal will keep the relationship healthy.  Plus "Marriage = Equality" it's much snappier and fits on a bumper-sticker better than "Marriage = Two consenting adults," don't you think?