I thought about this some more. I'm not sure why people need to question the mutually healthy and genuinely agreed upon relationship dynamic of adults. If you can do something that makes you happy and no one is getting hurt/manipulated or walked over than why not pursue that? Why do others want to rain on the parade of consenting adults?
Two main reasons I can think of:
A) it's not what they would do regardless of their partner's own attitude and therefore they can't understand the desire
B) they don't feel they could do it because of their partner's attitude and therefore feel supressed and angry at those who can and refuse to admit their secret desire.
I would ask them why your desires are causing them such distress? What need is it they have that requires them to understand or for you to conform to their ideals?
Playing the Game of Life with Monopoly rules.
Monogamy might just be in my genes
Poly Events All Over