Hi Wolfie...I do have a litle experience that might relate to your situation. Here is a link that leads to a thread on my struggles in trying to find peace around socializing in a much different community.
Missing Normal...Struggling, Loving and Learning
You've been very honest and clear that this relationship will come to an end if you find an exclusive one that fits you better. That is admirable and very mature IMO. If your partner understands and accepts this then there is no disrespect involved. So I guess you both have to decide if your criteria to be in a relationship can accommodate you wanting to be completely separate and them wanting to include you. If they are really adamant about you joining them within the community, then I would question their motivation a little...do they want to fit in socially by showcasing their polyness to others? Have they told you why they want this?