I try my best to not be one of those high-and-mighty poly people who just can't believe that people still form monogamous relationships and expect them to work.
I don't espouse polyamory to everyone, or even recommend it to most people I meet. I do answer questions people ask me about it, and I answer them in the most honest way I can. Do I feel like monogamy is good for humans? No. Does that mean I'm going to tell everyone I meet that they should accept multiple lovers into their relationships? Also no.
I'm also aware that just because a relationship is poly doesn't mean the people involved in it are good people. A good friend of mine and I always say, "we don't hate you because of your race, your religion, your sexuality. We hate you because you are stupid." There's stupid in poly, and there's stupid in monogamy. I think the ultimate offense is when people get too caught up in the "supposed to" of their relationship and stop actually communicating with each other. Okay, so you're monogamous. That means maybe you don't tell your partner about the elaborate sexual fantasy you had about the new person at work. But it doesn't mean that you can't communicate other limits or expectations. When Now-hubby and I first got together, there was the negotiations about what would make "us" exclusive as opposed to any other relationship we might form with somebody else. In retrospect, totally monogamous discussion topic. Which is where the lines blur and why I think a lot of the BS about what type of relationship you have is so unimportant. It's whether you're invested in your relationship in some type of intellectual way that matters.