Anyone who says they would form a new relationship in "retaliation" against you and who refuses to communicate cannot, in fact, "handle the poly thing". I think SC's suggestion to just co-parent but not date is a great one
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.