Why do you feel the need to protect the rigid existing social norms of relationships, families, parenthood, sexuality, gender etc?
Not sure what polyam has to do with fetishes, or even sex, really. They're just relationships like any other, it's just there are more partners than we're used to - equally full of mundane, everyday aspects of relationships like scheduling and doing the housework and bickering over Netflix.
Would you say a marriage between two people is primarily about a fetish? Or because it's the social norm, is that deemed the baseline on which everything else is built - and why does it bother you that someone might want to dismantle that?
Humans have been nonmonogamous for a long, long time. This isn't new. But social norms about marriage and monogamy (driven in part by issues of parentage, religion, and misogyny) have made the idea of multiple partners seem deviant or abnormal, despite there being good evidence for the fact that many people aren't actually happy or able to commit to monogamy. Why shouldn't be dismantle the idea that the '2 married people parenting their 2.4 children' (which often also skews heteronormative - hence the furore about gay marriage) is the 'right' way to do things?