It was kinda disrespectful of Erikson to not mention poly units such as mine (a lifetime poly-fi MFM V), but I guess complaining about that is a bit of a red herring. It's the more fluid poly households that Erikson wants to talk about, the ones where new partners do come and go often, the ones where children are exposed to that and can be affected by it. I suppose she's singling out what she sees as polyamory's weakness, but that's her perogative. So, let's talk about that branch of polyamory. And so far, the answer has been pretty simple. Any adult should be no more involved in a child's life than how long that adult will be around to be involved.
And the other thing is, adults pass in and out of children's lives all the time. What about their school teachers? What about a random police officer (or other adult) a child may greet on the street? What about grandparents that pass away? and most of all, what about platonic friends the child's parents have? Fallings out can happen, adults can disappear from a child's life, and that child may experience an owie because of it. But the only real difference in a temporary poly companion is the sex -- and that's actually not something the child should know much if anything about anyway! So, "Stop poly; save the children," doesn't exactly work as a bombproof argument.
Love means never having to say, "Put down that meat cleaver!"