Brian Pellott's review of a recent YouGov survey is interesting but very misleading. As with any survey, the wording is very important. Questions can be leading and biased. The results are only as accurate as the surveys construction. Unfortunately, none of the links in Pellott's "Most non-religious Americans condone polyamory, new survey finds" lead to the actual survey. I also could not find a copy on my own so I do not know how the questions were worded. What I can tell from his review is that within his own mind he has conflated a variety of interrelated but separate aspects of the issue being surveyed. He mixes together morality, ethics, criminality, personal views, and public policies among various others.
The conclusion that:
"25 percent consider polyamory, which YouGov defines as the practice of engaging in multiple sexual relationships with the consent of all people involved, morally acceptable.
14 percent consider polygamy, the marriage of more than two partners, morally acceptable."
May or may not actually reflect people's opinions since I can't analyze the questions they answered.
All I can really do is use my personal views to demonstrate these conflations. Personally, I do find polyamory immoral but not necessarily unethical and certainly not criminal. I find it hard to believe that more than two people can be as devoted to each other as a couple. I could be wrong but if I'm not than one or more involved in such a poly-amorous relationship would be, in a manner of speaking, second-class. I firmly believe that all should be equal partners. Claiming to love someone and then treating them as less important than yourself or another I find dishonest and potentially harmful.
With that pointed out I would add that this is not automatically unethical. The reference to "consent" in the conclusion is essential for my accepting such a relationship as ethical. If each adult involved understands and accepts the relationship they are entering into I see no reason why I should object. When it comes down to it, other people's romantic relationships (assuming they are consenting adults) should not be any of my business. It is a private matter. The government should also not be prohibiting or criminalizing it. This, however, does not lead to the notion of condoning it. I also don't think it should be given the same legal status as a marriage.
Basically, I personally disapprove of the idea of polyamory but see no legitimate reason for it to be either officially condemned or condone through public policy/government intervention. I wonder how many answering the survey answered the way they did because they also did not wish to outright condemn the choices other adults have made for themselves. I can easily see how I might have answered a survey in a way that would skew towards the false conclusion that I find polyamory "morally acceptable".