Recently an acquaintance of mine reported her friend's girlfriend dumped him. Why? Because the girlfriend didn't like her boyfriend being friends with someone in an open relationship. Today I'd like to talk a bit about similar situations I've seen, and similar awkwardness I've encountered personally.
Your spouse is friends with a poly person.
First, "ruining others' relationships." It's not a thing we do. Every poly person I've encountered abhors cheating. If someone's not consenting that should be, we don't engage in that relationship. There's exceptions, of course - but it's an extremely small minority. It's the same reason why most poly folks don't enter into "don't ask, don't tell" relationships. The best case in that arrangement is that we ruin a relationship and cause pain to someone we love. Worst case? Our relationship gets ruined and we cause pain to someone we love as well as ourselves. It's a dumb move.
So what's really happening most of these situations is a monogamous person is insecure, uninformed, or afraid. Maybe they don't understand what it means to be polyamorous - they could confuse it for being amoral sex fiends. Maybe, as was the case with me back in the day, they're closet cases and lack the information, safety, and courage to try it. Maybe they're thinking about cheating and projecting. Or maybe they're just not happy with the relationship and are looking for an excuse to leave. Regardless, the polyamorous person has nothing to feel bad about; but it hurts us to see our friends hurt - just like anyone else.
I've had husbands talk to me about it. That's a reasonable thing to do; and I try not to take offense when it happens. Most of the time they're just trying to make sure I'm respecting their relationship, them, and their spouses. That's totally cool. As I said, I'm not a homewrecker and I don't know anyone who identifies as poly that is. If you're uncomfortable with the idea of being polyamorous, or being in a relationship with someone who practices it, you should totally say something to people who might potentially bring the subject up. Communication is awesome. Husbands who bring up their concerns in a respectful, open way are good duders. I imagine wives who do the same are too - not many wives are concerned with me personally trying to 'steal' their husbands.
Your friend/family member is a poly person.
These folks can be irritating. I've heard several of my friends say "Polyamory just doesn't work." "This is a phase." "You'll find the right woman." Things like that. Hey, thanks for trying to invalidate something personal I've told you about myself. What a pal. I think these people usually mean well. Maybe they've experimented with polyamory and it didn't work out for them. Maybe they knew other people who did the experimenting. Mostly, I don't think they understand I am happiest when I'm free to explore my emotions and relationships.
My 'outing' as a polyamorous person came along side another major change in my social circle. It's hard for me to determine which friends I lost because of the poly thing, and which I lost because of the other thing. I do know the people who still associate with me are mostly accepting of the way I love. They may have concerns or think I'm kidding myself, but I know they have my best interests at heart. I would prefer it if they avoided telling me how I feel is incorrect; but I guess I prefer knowing what they think.
Your romantic suitor is poly.
I bring up polyamory early - before the first date if at all possible. I don't want anyone to feel trapped or tricked. Most of the time this ends the conversation. Doesn't matter if we appear to be soulmates up to that point, "I'm poly" might as well be "I'm into fucking mountain goats" to a lot of women. There's nothing to do there. A nice part about bringing it up early is not wasting a lot of time.
The next most common response I encounter is, "Aww, too bad I'm not." You don't have to be. I suppose they might mean "I'm not willing to date someone who's dating someone else."To me that seems like a separate issue. When I was monogamously wed there were fights every few years over someone developing feelings for someone else; both parties responsible for the emotional infidelity. However, I personally would not have cared about hers if she were honest about them. Hell, I probably would have been supportive if we acknowledged it was a thing ahead of time. I'm not sure if she'd feel the same. Still, it is possible to be involved with a polyamorous person while not being polyamorous yourself. It's like refusing to date a bisexual person because you're not bisexual yourself. Say you're not comfortable with the potential for jealousy; or say "I'm not interested in dating you" if that's what you really mean. I do think a lot of people would be surprised by how little jealousy they actually feel when their emotional (and physical) needs are met.
The final annoying response I get in the dating scene is along the lines of, "We can try it, but I expect to be monogamous when we get serious." NEWP. While I could do casual relationships with people I already trust, I'm not typically looking for someone to fool around with. The idea that I could be changed by the right person is pretty off-putting. One woman recently phrased it as "Let me know if you change your mind on that, because I'm end game." Lady, polyamory is my end game. The best you could get from me is a lie, and I don't want to live a lie. This is a problem for dating beyond polyamory - don't think you can change people later. You accept them as they are, or you don't date them.