Being in a small town Tonberry and I have to be careful, so I've been carefully testing the waters about who is going to be judgemental if and when they do find out.
So a few days ago I got a speel from a coworker about how open relationships never work out, either the couple will close off or they'll break up because the relationship wasn't working, that people can't be serious with more than one partner, and so on.
I had a little fun with her, though. I pointed out that not so long ago, people were saying the very same things about lesbian and gay couples... and she immediately got defensive about the subject, she has one sister who has been out for years and another who is in her first same-sex relationship right now. I pointed out the correlations that prejudice have on the stability of relationships, and how there were so many long term same-sex couples that people claimed were "roommates" or "best friends" for decades, then asked her to imagine how many people there might be hiding multiple partners under that cover.
I don't think she completely got it, but I at least gave her something to think about.