It depends on the circumstance - there are times when DH may jump the gun and disicpline one of the girls for something they haven't done. If I have proof of it - I will calmly act in defense of them in front of the kids. Dh will then apologise to whichever dd - and back down. I think in this instance it's good to hear their Dad say sorry to them for misunderstanding.
On the weekend though - we handled a situation very poorly - in front of our eldest - who is 7. We reflected afterwards though, which I think is very healthy for all of us.