Most people that are for monogamy don't often think non-monogamy in it's many forms work at all. They could be against it for religious reasons, moral reasons, or any number of other reasons. Monogamy works for them. You should be with one person in a relationship and only that one person through the duration of the relationship. Multiple partners? Swinging? A husband and a boyfriend? Nope, that can't work. Human relationships are too complex when it's just two people. Adding more to the mix? Disaster. Of course, there will be jealousy. Feelings will be hurt. It just doesn't work.
Most people that are for a form of non-monogamy don't often think monogamy works. It doesn't work for them. It doesn't work for so many people they know. Humans just aren't meant to be with only one person. It's biological even! It just doesn't make sense to stay with one person. Having a wife and a girlfriend works just fine for us. My husband and I going to swinger events and finding mates to play with is great for us. There are so many different ways to do non-monogamy and it's not wrong, not at all. It's not weird and there's nothing wrong and it does work. Monogamy is so outdated. Monogamy doesn't work. If you want to be "stuck" in a relationship with one person and only that person? You must be kidding yourself.
I get so sick of people for monogamy going on about how it's the way to go. The only way to go.
I get so sick of people for any form of non-monogamy going on about how well it works for them and thus if you would just try it then hey, it'll work for you too!
My own take on it? Monogamy works.... for some people. It doesn't work for other people. Non-monogamy works.... for some people. It doesn't work for other people. You and your partner have to figure out what works best for both of you. Discuss it openly and honestly and respect the feelings and opinions of your partner. If non-monogamy is something you really want while your partner is dead set on being monogamous? Maybe the relationship needs to be re-evaluated.
I get why people feel a need to defend their choice. Especially if they feel like they're being attacked by it. Turning around and trying to prove to someone why they're wrong and you're right? Doesn't help.
Why can't both sides understand and accept that neither way is the right way or the wrong way? There isn't a way that is right for every single person. It's about what works best for you and just because something works well for you and 159 other people you know doesn't mean it works for the rest of the world.
"It really gets under my skin when someone is convinced their single experience is tantamount to the entire topic, period." (Thank you, Tragic. ;D)
P.S. I'm not saying that every person who has ever had this discussion, wrote a post on it, etc handles it in such a narrow minded manner as "this is wrong, I am right" but it is handled in such a way by a huge percentage. On both sides.