This post was transferred from my original blog
This is an attack on polyamory. I'm not poly, but I have many friends who are. The entire argument seems to be that it will negatively affect the upbringing of children:
"Once the principles of monogamous companionate marriage are breached, even for supposedly stable and committed sexual groups, the slide toward full-fledged promiscuity is difficult to halt."
My entire reaction to that is: So What? It might mean more promiscuity, but I think you need to prove there's something wrong with promiscuity.
"Polyamory websites are filled with chatter about jealousy, the problem that will not go away."
So is nearly any discussion of monogamous marriage.
"Once monogamy is defined out of marriage, it will be next to impossible to educate a new generation in what it takes to keep companionate marriage intact."
Companionate marriage is, itself, a deeply unstable institution. Economic, arranged marriage, is stable - as long as expectations are low enough. Though it's well worth remembering that the arranged marriage era is also the era of the formally established official mistress.