1st of all, i would like to say incredible debate....(applauds) saibot and moses has both really good points and i do agree with the both of your points.
But one have to ask... True love how do you even define that? There are plenty of definitions to love and just because you are in an open relationship doesn't mean you are not experiencing true love.
True love in another definition is a person that is devoted to their partners. But devoted to their partners and being sexually active is a different thing altogether. The man/woman in a relationship may not want to be tied down and be trapped. Humans are animals, they can't really stay put. Having an open relationship just means that you can have fun and date around with other people. Like saibot previously stated:
What about some sexual needs that a certain partner never will be able to satisfy by himself/herself no matter how hard he/she wants it or tries?
That is a very good question.... in a closed relationship one may not be fully satisfied with one's partner sexual technique and may want more 'experienced' technique. They may not be satisfied but they love their partner, this place them in a very difficult situation. If a person is not satisfied, we all know that there are a few odd consequences.....
Here's an example: Say a man is not satisfied with his partner's breast/felatio/etc. then comes a woman that can satisfy him and starts to seduce him. Guess what will happen next..... The man and woman will end up in a love hotel and when his girlfriend/partner/wife/etc. finds out this will become a heated arguement and ultimately ruining their relationship.....