I have on occasion heard of someone commenting that it is good for parents to fight in front of their children, so that the children will be prepared to fight properly in their own marriages without freaking out that something is wrong with them if they fight. On the other hand, I have more often heard that parents should never fight in front of their children, in order to present a united front.
Then there is the Miss Manners view, which is that you should fight in front of them, but in a foreign language, to increase the educational value.
I'm a bit skeptical of the former view, but can't quite put my finger on what is wrong with it. I would think it would be pretty hard for a husband and wife to fight publicly in a way that showed proper reverence and love, but I suppose it's not theoretically impossible.
We do expect to frequently disagree in front of our children, on such matters as public policy or literary interpretation, and indeed to encourage them to stake out their own positions as well. However, I suspect this is not what is meant.
Naturally we don't want to omit an important part of our children's education. But it would be difficult. First, we'd have to find something to fight about. Then we would have to want to fight. (I'm a middle child. I don't fight, I manipulate.) And if we had to do a foreign language, too--I suppose pig latin doesn't count. Perhaps our children will just have to miss out.