Again, I think education has a lot to do with it. Poly may not be mainstream and very different, but a person who has been trained from a very early age not to pre-judge people and things we are not familiar with goes a long way. It may be surprising, unique, interesting--maybe even a little scary, but generally something they want to learn more about before making a personal judgement.
And then there are thoses rare gems who, despite an upbringing that did not encourage tolerance for those unlike us, are seeded with the gift of empathy and compassion and manage not to carry the prejudices they were taught by their elders as children.
The burden to teach now falls on us: we must help break down the barriers by being positive examples and role models of poly living. No, we do not all practice poly the same way. There is a broad spectrum of practices by those who define themselves poly. I think now that we are in the multi-media age, the walls may start to come down a bit. We have more than the one-sided, sensationalized vision of what poly is that is painted by the networks. We have bloggers and boards and YouTube and a Twitter; we have Facebook and Kindle and Amazon; We have a thousand networks now, and my guess is there is more than a few who are more than willing to portray positive poly relationships.
Times are changing. This is an exciting time. Change takes time, but I think we will see poly finally recognized as a non-evil expression of love. Love, in the end, is love.