I stopped to think about it, and realize I've managed to have intimate relations (read: sex) with almost every cultural variant there is, at least in their most extreme forms. Did I do it because I felt obligated to foster the tolerance and diversity through polyamory?
I did it because I found them attractive and desirable. I'm not going to insult the intelligence of anyone by trying to claim that I didn't notice the cultural and physical differences, nor will I say that those things didn't have an impact. Of course they did, for good AND bad.
I think the only "obligation" (if it could be called that) of a poly individual is to not let those differences stand in the way of a relationship that feels right at that almost zen like fundamental level. That could even include the tendency to fetishize an attribute of any sort (including, it should be noted, gender) in ways that hold you back from relationships that don't fit your self image. A dyke might find that one man who makes her blood sing. A woman who's only into black guys might find herself falling for a white guy. And yes, both those items are from personal experience, and sometimes people refused to let themselves enjoy something good because it called their personal identities into question.
Zen...I think I just had one of those darn flashes of insights.
Nothing comes across faker then a relationship designed for show or obligation. Well intentioned fostering of a force for good does NO ONE any good. It's one thing to push past restraints placed upon you by society, another to place whole NEW restraints placed on us by ourselves.
Here's an idea: Let us consider each of us a culture unto ourselves, take what works, invent whatever new things we need, discard the things that don't (or no longer) work, and keep our minds open to the possibilities.