You have heard of the idea that our past makes us who we are right? Yeah sure, I accept that there is a plethora of various polygamous open relationships in Los Angeles but in my life, I've only ran into the types I mentioned. However, because of my experiences I've developed a negative view because I simply look down on men and women and their idea of free love. That is my opinion. For the sake of this discussion I am not saying I look down on you because I don't know you. I am only defining what I want and don't want for myself.
Defining and knowing what one wants for oneself makes sense and it's what everyone should do.
Your experiences will of course shape that, but when we're talking about an aggregate situation - open relationships in general - and you're given new information, it makes sense to incorporate that new information into your preconceptions rather than insisting that all women/men/open relationships/turtles are the same.
It is illogical and philosophically difficult to produce demonstrative proof that fidelity on an open relationship level is the same as monogamous relationships. I mean, there are gray areas and I've exposed one gray area
One cannot prove a negative. *
Instead the proof is on the claim that there is a significant difference.
How have you exposed a gray area? Your assumption was that if you were in an open relationship you wouldn't feel any sort of responsibility towards fidelity. That is a flaw in the hypothetical "you" not a flaw in the concept of relationships. Obviously some people feel the same about monogamous relationships or there would never be any cheating. Infidelity's a relationship problem, not an open relationship problem.
ETA: *Research in the area of polyamory is ongoing. There aren't that many studies at this point that could actually prove a lack of difference.
Also polygamy =/= polyamory. There are connotations to polygamy - religious, misogynistic, oppressive, abusive that though not always true are so ingrained in modern society that polyamorous people - who are incapable of marrying and thus being polygamous - willingly separate themselves from the term.