"Poly" wasn't the only issue here.
These "unicorns" were young...in their 20s...often an idealistic age....not always very realistic in terms of what the world "should" or "shouldn't" accept.
(Nothing wrong with idealism, per se, as I'm still called "Pollyanna" at 56 years old....but it has come at great cost to me at times!)
Their parents didn't know they were bi-sexual in some case, much less poly.
No...most of America isn't ready for poly. But much of America wasn't ready to give women and Blacks/African Americans the right to vote and to own property either. It didn't stop it from happening eventually, but there was certainly a lot of pain, loss, and sacrifice along the way. Many individuals paid a high price in speaking up for what they believed to be the right thing.