When it's a POLICY enforced by a man onto his female partner, that she can only have same-sex liaisons, or additionally must "share" her sex partners with him like toys, but he can have sex with whomever he wants, rather than an AGREEMENT that everyone is happy about (and not just agreed to and put up with until the guy gets past it), a One Penis Policy is a double standard that is ALWAYS sexist, selfish, controlling, and dismissive of women. It would be a lot easier if the OPP-enforcing guy would just announce how chauvinistic and insecure he is, and then go work on it. As someone else said, read a little bit more around this forum. Here are some links to some good, thoughtful threads here on OPPs, which will give you more perspectives on it:
One Penis Policy
OPP, unicorns, and derogatory poly terminology
Cloudy, FWIW, I thought Vinccenzo's post in this thread was the most important one for you to digest regarding the underlying patriarchal beliefs that are ingrained in our society. Those beliefs are like default programming and they come into play in insidious ways. The dynamic she described is so relevant, so common, and very much a part of what is drilled into the male mind (at least in western society)! What she described is usually glaringly obvious to everyone surrounding men like you who only want a OPP - yet you immediately discarded her suggestions! That even says a lot -- when people ask for UN-sugar-coated truth and then immediately dismiss something out of hand without even considering it, that means a nerve has been hit! But for self-preservation, the blinders must stay on! I would suggest you sit with her post and let some of it sink in, and drill down into your psyche with deeper questions about attitudes, not about your girlfriend and how much you love women and enjoy their bodies in bed with you and her, but about the beliefs instilled in you, fears about threats to one's manhood, what it means to be a man, possessiveness/ownership/dominance of men over women, and old patterns of thinking. Seriously, what you are talking about is deep shit and should be examined more closely in an"inner knowledge seeking" way.
Also, I have another question for you. What if your GF was straight and NOT bisexual, but came out to you that she is poly? She would only want to be with men. Would that end your relationship? Would you still tell her she has to be with only women and expect her to bring women home to have sex with you, too? Or would you discuss the possibilities and start working on your inhibitions and insecurities about it to see if you could accept her having the kind of love and intimacy she wants in her life? Since poly is about love and not just sex, why would the genitals of anyone she's interested in matter to you, really? It's her body, her heart, and her life. How can it sit well with you that you are dictating who she can share herself with? As I see it, if she wants to share herself with a man and you don't like it, the work to be done is all inner stuff on your part -- to come to terms with your fears, insecurities, and need to be in control, but it isn't about imposing rules on her, a grown woman who is free to choose how she lives her life and whom she wants in it. Shackles may keep her close to you, but they eventually leave bruises and scars.