I go away for one weekend...
A couple of things to address:
1. No poly person I know has the time or energy to date 15 people. It's a pretty ridiculous hyperbole. I know people who might have what they call "sweethearts" who are perhaps ex-lovers that they're still friends with and may or may not occasionally rekindle something with but who they do not have an ongoing relationship with because of whatever variety of reasons. I still don't know anyone who has fifteen of those.
The limiting factor in monogamy is typically love or commitment. The limiting factor in polyamory may be commitment, but it is very often time/energy. I could love more people than I'm dating but finding the time for them isn't necessarily in the cards.
2. There are very few people who are completely monogamous - one partner and one only throughout their lives. Even in those monogamous relationships, people have plenty of other people in their lives. Poly people just find themselves capable of loving some of those friends, coworkers, etc also.
3. A good comparison is that just as I can have more than 2 kids or more than 2 friends and still love them (and I do love my friends, I'm just rarely in love with them.) equally and for different but similar reasons, I can love my partners equally.
4. The reason why communication keeps coming up is that successful polyamory absolutely requires increased open and honest communication from the typical monogamous relationship. I've been in both types of relationship and the difference is striking. It means speaking up over even the little things and knowing that your partner won't think you're being petty and nagging. People who aren't successful in poly rarely remain in poly. Either they can no longer find poly people who want to date them because they're known for not being honest or not communicating, or they give up because "poly doesn't work."
So all the people going on and on about "magic" poly people miss the point. It's self selecting. If you don't follow the rules, you quit.
5. Even naturally polyamorous (People who see it as an identity they were born with not just a relationship style) people can choose to be monogamous. It is a choice I would make for my primary boyfriend if he needed it from me. It's a choice he doesn't ask of me, because he knows that it would be as hard on me as my polyamory is on him.
6. If being loved and loving others is "decadent" or "hedonistic" I don't really know what to say to the person thinking that. If I made every decision out of pleasure only, I wouldn't be poly, I'd be single or mono and a cheater. It's way easier. It does feel pretty awesome to be loved and to know it, but you can have that feeling in any relationship style. If that is decadence then asceticism would be isolation.
7. To come into this thread and lecture on STIs is similarly baffling, STIs were not the topic of the thread and would have little to no bearing on which is more "natural". Poly people are aware of STD risks and again, this is a self-selecting phenomenon. Individuals who are NOT on top of their STD tests, who do NOT use condoms or other barriers when that is a relationship rule. Those people don't last in the poly community because they are untrustworthy.
8. Poly people are not perfect, there are liars, there are cheaters and there are people who come to poly to get their own rocks off rather than to actually be in a relationship with other people. However, as I stated before, the community is pretty good at recognizing those individuals. I was just talking the other day with my other boyfriend about a lady he was interested in dating an how her "don't ask/don't tell" attitude is a problem for him because it feels dishonest. He's understandably wary about pursuing anything with her. But no polyamorous people claimed they were perfect in this thread. The only people making these claims were people mocking polyamory.
9. My boyfriend is not my "primary" nor is my other boyfriend my "secondary." They're usually just "Name" and "Name" but I choose not to disclose their info on the internet, so "BF" and "Other BF" works just fine. Currently my poly relationship is however more hierarchical than I prefer, but that's a function of working through things with a monogamous BF. I simply think that soul mates aren't limited to one person. I describe people as resonating with me, as if you pluck a note on their harp and I can feel it within me, and vice-versa. We fit well together.