My question is though: if there is an ideal of equality to be fought for with respect to polyamory, what does that look like? Is it freedom from legal persecution and the practice of discrimination from such real world things as employers?
I don't advocate for "equality" in the modern political sense. I advocate for "voluntary" and "consentual".
I beleive every human being: child or adult, man or woman, gay or straight, asexual or pansexual, poly or mono, rich or poor - has the right to associate freely. I believe they have the right to contract in whatever arrangements they want. A couple buying a house together, or a group of friends forming a commune. Two men marrying, five men and two women marrying.
But I don't think ANYBODY should be forced to respect the associations you and I make when they have NOTHING to do with those associations. If an employer doesn't want to offer benefits to a gay married couple, I think that should be their choice, just as they currently have (or SHOULD have!) the option to provide NO benefits to their employees.
People value respect and diversity. If people were free to associate and contract as they see fit, and likewise, able to ignore other people's associations as they see fit, you'd still see social regulation. You'd see people boycotting and protesting companies for denying homo benefits but offering hetero benefits just as you see today people boycotting companies that choose to use fur on their models in fashion ads.
If you want to see poly equality in terms of marriage, you need to remove the state from marriage. As long as the state (and the laws, and the violence behind them) sanctifies ANY kind of marriage it must inherently ignore (and be unequal to) another kind.
The same is true of employee benefits and anything else that would make poly "unequal" today.