If you think about it, I think what you are observing is just typical for human nature. It's just the ego interfering as usual. It happens in all areas of life. Anything from a neighborhood you move into to the latest hybrid car you drive etc.
People tend to feel they've discovered this leap in evolution and everyone else is lagging behind.
I do think this exists in life/love style oriented choices also. Monogamy appears to be a very "broken" system and there's been lots of discussion about it for a long time. For those that feel they've transcended this 'brokenness', they let their ego boost them up a notch.
You have to remember, people love to speak in broad generalizations and that's really all it probably amounts to. There are, and always have been, many successful (semi?) mono relationships but it's a numbers game. I'm just going to pull a number out of my arse - say 10-15% success rate, which IS dismal. So people get caught up in now not belonging to that failed 85-90% and think they are special.
Human nature. Let it pass