I'm all for being open minded, but only to your comfort level when you are involved. I'm with you I wouldn't want to be part of an "open relationship" but if others do great for them.

Your problem is that one of you are going to have to give in to the other's wishes or your going to break up.

I do think you sometimes have to compromise and give into other's wishes at times in a relationship. But there is a HUGE difference between not having a sexual fantasy fulfilled, and being pressured into a sexual encounter that you don't really want. We all have fantasies that will never happen (such as winning the lottery), you need to make sure you don't get pressured into something that you will regret.