I think some of the defensive ess comes from people who are percieved as being in dynamics with primary and secondary partners, have couple privilege tossed out in their face when in fact their lives aren't that simplified.
For example: people assume Maca is my primary because we are married. But I was with GG 20 yrs, Maca 14. I have a child with each. We all live together, finances are completely joint, custody of ALL children is joint to ALL of us....
GG and I have a different relationship than Maca and I. But one is not less primary than the other. They simply differ because preferences in each couple differ. I have couple privilege, twice over. I'm "double couple privileged" I guess.
"Love As Thou Wilt"