I was confused over the title but after reading your response to the other answers I think I am understanding your point. The breakdown of the traditional family is what is changing family values. That is not to say that a single parent, male or female cannot raise their children properly and raise them to be good people with good values.
In generally speaking though I see the point you are trying to make in that by not having the influence of both the male and female in the household or at least in the lives of the children, they only see one side of a belief system. The mother having one way of thinking while the father would have another way of thinking. It doesn't mean that either one is bad or right for that matter but by not having both thought processes to see a point of reference from just the one, there becomes a breakdown.
An example might be a situation where a single mom that is doing a good job raising her child, a daughter is allowing her daughter to go out with friends and she is dressed borderline of being slutty looking. If the mother not thinking the way a father would, allows her to go out looking borderline like a slut, she might come to believe that she looks appropriate and that it is ok to go out looking that way. On the other hand a father in most cases might look at the way she is dressed and he will put his foot down and say to her that she is not going out that way. He will make her look more conservative and less slutty looking. Understand that I am not saying either opinion is right or wrong but it brings 2 different opinions to the forefront. This is what will help the daughter grow up with certain values. She will understand how other people see her and that will allow her to make better decisions in the future. By missing either one of those opinions does not give the daughter a true perspective of reality in the real world. She goes on believing that it is just one way only.
Consider if her father was raising her by himself how she might grow up making decisions. It might not be wrong for her father to tell her to dress differently, but she would also not have such freedom of expressing herself the way that she wants to. With both parents' input she will be more equipped to make reasonable decisions by being able to understand where 2 sides of an argument are coming from. Neither one is wrong, but they are different and compliment each other.