From my own experience, people who are bisexual tend to have gone through a period of introspection and self-examination to arrive at the conclusion that they are bisexual. Along the way, they find things like polyamory. Additionally, being bisexual also means you are more likely to come into contact with the idea of polyamory.
I'm personally not bi. I don't have the "ick" response that the vast majority of heterosexual men I've dealt with have when talking about sex or intimacy with other men or attractiveness, I just simply don't find other men attractive.
I am as direct as a T-Rex with 'roid rage and about as subtle. It isn't intended to cause upset, I just prefer to talk plain. There are plenty of other people here who do the nice, polite thing much better than I can. I'm what you'd call a "problem dinner guest."