Julie would learn how to take advantage of her friends and family when there was something in it for her. She would learn how to disregard others' suffering because she had a right to enjoy life to the fullest. All wayward spouses hurt the people they care about the most. Wayward spouses rationalize that they had to look out for themselves which is why they developed the relationship outside of their marriage in the first place. Their actions seem to benefit themselves in the short term, but it has disastrous effects on members of their family.
Marital discord is hard enough on children.
It undermines the basic security needed for them to learn and grow. But to add infidelity to a troubled marriage turns a problem into a disaster. Parents who have an affair are teaching their children very important rules that are likely to be followed for the rest of their lives. It ultimately not only undermines their marital relationships but it also seriously hurts their own chances for success in most other areas of life. To do otherwise is not only terribly irresponsible, but may tend to perpetuate the learning of these rules of deceit and thoughtlessness for generations to come.