Not true - honesty and ethical behavior is a central aspect of all ethical non-monogamy. It is quite possible to cheat in polyamory, or in swinging, or in any other form of non-monogamous behavior if it isn't being done openly and honestly.

BTW, you don't need to keep attempting to explain this to me. I've been polyamorous for a long time, and have had several pieced published in Polyamory Today, and other related publications.