I suspect that most people assumed that with the back story and the way the open relationship was proposed, Nicole would have sex with someone else. Some people will be fine with this, and others will not.
My issue is (before the upcoming change), you either had to accept an open relationship with no notice, discussion or understanding of what she wanted / expected or you had to remain faithful (and hope she did). I have never been in an open relationship, but assume that they come about due to an agreement between both partners (including any rules) and not an ultimatum.