We just don't like each other much. I mean, we like the "good" people that we know in our personal lives who are just misguided, but we have reached the level where there just not is much grace available for "insert generic political opponent here" anymore. We really just view the world too differently right now...in the past there used to be some common bonds that held us together but many of those have been tossed aside or are slowly being eroded. We don't view justice the same. We don't view our past the same. We don't share a common civic religion anymore. All social bonds have been under assault to the point where we do not even agree on what marriage is, what a man or woman is, etc.
If we were a couple we would be long past the point of our friends telling us we should just divorce so we can both be happy. We have so many irreconcilable differences at this point where every conversation about problems just ends in a laundry list of what we did to each other. We all have our "Yeah, that was bad but remember that time when you all did..." This is just a marriage of convenience now.