I'm not talking about day to day disagreements. I think healthy disagreements over things are good for kids to see. Shoot DH and I a disagree on a lot of things and love a good debate between each other. He is a hard core republican where as I am more liberal so it can be very heated around here at times..lol I can only go off of my experience and DH's. My parents disagreed, my parents got upset with each other but it was was done in a healthy way where it was. Then DH had parents who fought and while in some points it was abusive. I mean we could all be going somewhere and his parents would have an all out fight in the parking lot to include physical abuse or verbal abuse. I used to work for them and I was put in the middle of their fights. It was very unreal to me because I saw my parents fight however not to that extreme. When it came to things that related to us kids. my parents always backed each other up and then discussed it in private later if they felt things needed to be done differently. Where as DH's mom always stepped in when she shouldn't have and the times where she should have she never would. Of course DH came from a very abusive home. Both his parents were abusive to each other and these are all things we are working at with DH. Because he blocked a lot out and now having DD he is remembering things and trying to make the changes he needs to so she never grows up thinking that what he saw was normal. Then on the other hand I have a BIL who to this day has never seen his parents disagree on anything. He has no idea how to handle confrontation or how to disagree/stand up for himself. He is getting better but still is a work in progress.
I also mean more in a situation where like if DH felt something DD did deserves for her to be grounded and I felt like well I think your over reacting. I don't think its wise to have that discussion in front of DD and I need to back him up at that moment. Things like that.
new2this, in reference to what you said about a united front, I used to think (before having kids) that my husband and I should never disagree in front of the children.
Then I had my had my own children and learned how very difficult it would be to ever have any real conversations if we saved all big discussions for the approximately ten or so minutes a day that we were both awake and our children were both asleep.
I do believe in disagreeing respectfully and not raising our voices to one another if we can help it. However, I now actually think there's value in children seeing that Mommy and Daddy can disagree and sometimes they can even get mad about something, and yet they still love each other and still stay together.
I also no longer see the term "united front" as a good analogy for the parent-child relationship since we are not at war with one another.