The man was carrying light hunting gear while his wife carried the baby and a heavy swag. This upset Nancy because the woman should still be resting. She stopped the car and explained to them what was on her mind. The woman kept completely out of the conversation and her husband ignored Nancy's advice and went on his way as before, followed by his wife. The man resented Nancy because she had made his wife take a decision without consulting him first.
Aboriginal men are generally inconsiderate towards their wives.
In Aboriginal society a man is not normally expected to do a woman's job and a woman is not expected to do a man's job. In Aboriginal society there is a fear relationship rather than a love relationship between husband and wife in which the wife does as she is told. It is not likely that the man resented Nancy for this reason, firstly because Nancy had contacted him and secondly because he appeared quite happy before she asked him to look after the baby. Since there is no indication in the story that Nancy had a poor relationship with the people you cannot assume that he would not have accepted her explanation. If anything he would have been angry with his wife.