These kinds of people make me crazy - putting forth half-baked BS just because it validates their bias. In truth, although some 90% of bird species are socially monogamous, genetic and behavioral studies reveal that in some species up to 75% of the offspring may come from “extra-pair copulations.” In other words, social monogamy does not necessarily equate to sexual monogamy. Also, most birds mate for a season, not for life. True sexual monogamy is almost non-existent in the animal kingdom because overwhelmingly, it’s not a good reproductive strategy.

Is Monogamy ‘Natural’ for Humans?

And if you can't differentiate polyamory from swinging or as you said, from cheating, you have no business speaking about it at all. Very frustrating!