To follow up on my earlier post -- since monogamy is the norm, poly takes a certain ability to break away from norms. If people are willing to examine the way they love, they are more likely to also examine the way they think and react. Also, the ability to manage your jealousy is invaluable in poly, whereas it's more possible to skate by with uncontrolled jealousy in monogamy.
For both of those reasons, I think you're more likely to find poly people who have examined their darker feelings, especially jealousy, and worked on managing them. That causes a false perception that requiring monogamy means you haven't examined yourself and aren't managing your jealousy.
But the way I see it, the enemy is the all-too-common tendency of people not to examine their modes of living and their thought patterns. The enemy is not any particular feeling or mode of loving. So to say that the need for monogamy is driven by unhealthy (to me, unexamined and unmanaged) jealousy is to mistake correlation for causation.
Me, 30ish bi female, been doing solo poly for roughly 5 years. Gia, Clay, and Pike, my partners. Davis, ex/friend/"it's complicated." Eric, Gia's husband. Bee, Gia and Eric's toddler.