Originally Posted by Tonberry
If everyone is happy, I see no reason to comment on how they decide to lead their life and relationships
I think we can state that some ways of living demonstrably foster the well-being of everyone involved, at least when compared to others of a less than desirable nature. Living on a farm in an area safe from most wars or dangerous animals would probably foster greater well-being than living in... say... a POW camp. Someone would surely play devils advocate and say that isn't true, we'd haggle back and forth about it and likely come to discover that living on a safe farm is, in fact, more conducive to happiness and health than being tortured daily in a POW camp, at least in a number of ways.
(Note: I used extreme examples to illustrate the discussion of comparing lifestyles, not as a value statement of monogamy or polyamory)
As reasonable people we can have similar discussions about living arrangements and determine the objective qualities of these different arrangements. Monogamy and polyamory are two such states in which we can attempt to come to objective understandings of how these two arrangements can work. We don't necessarily need to make judgment calls about them, but if discussed rationally and thoroughly enough surely there can be some aspects which we deem more likely to promote well-being than others.
For this reason I say there does not need to be unhappiness in a relationship in order to discuss it. Happiness is a difficult state to quantify so we break it down into discussing respect, independence, gratitude, jealousy, coercion, etc. As we trudge through these conversations we might discover objective truths which we were previously unaware of.