I think whether you feel positively towards the idea of Polyamory in your own life, or not, is just fine. It's unfortunate that some people feel the need to criticize others' lifestyles, though, and apply their personal morality to others.

It's precisely that type of thinking, that disapproving of others' mutually-consenting sexuality, that leads bdsm people to need to be anonymous on forums like this. And yet even some of us are doing it! Makes me very sad.