Acceptable infidelity?

I did not discuss the 'acceptable' times where for me infideltiy shouldn't be called 'bad behaviour'. For example, if somebody was in an abussive marriage and fell in love with someone else, if this led to them having sexual interactions with someone other than their partner then i would not class this as being wrong. As humans we have this abilty to sympathise and empathise and if i had ever been in that situation with an abussive husband (god forbid) then i would not class the infidelity as wrong.