The most unwise thing that a parent can do is when mom is disciplining the child or giving the child proper punishment for wrongdoings, dad jumps out trying to be the “nice guy.”  Good timing. Or the two are inconsistent in their approach to the perceived problem. 

Another things that can happen is when one parent has problems with the child, he blames the other for his failure as a parent. “See she does not listen to me just because of you,” as if he were free from blame.

To be sure, when a parent is having difficulty handling the child, the last thing she wants is being blamed or getting negative comments from another parent.

Of course, the dreamland would be mutual respect between two parents and the child observes and learns to be respectful.