It is certainly possible to argue that our behavior can be explained completely by socialization. To make this argument, we would essentially have to say that nurture is responsible for making us who we are and that nature has no part in it. I do not agree with this argument.
Socialization can be defined as the process of teaching us how we are supposed to behave as members of our particular society and culture. When we are born, we have certain human instincts, but we know nothing of our culture. We have to be taught our culture in the process of socialization. In this process, we are taught by our parents, our teachers, our friends and classmates, and even by things we watch on television or books we read. This process (we can argue) defines our behavior because it teaches us exactly what it is that our culture expects us to do. We then base our behaviors on what we have learned.
I do not agree with this argument because I believe that nature has a part in determining our behavior. I believe that we are born with some aspects of an individual personality that help to influence the ways in which we behave. If socialization explained all of our behaviors, there would be very little variation in human behavior in a given culture. Everyone would behave in roughly the same way. This would be particularly true within families, where parents can socialize everyone in the same way. But this is not how the world is. Individuals definitely have different personalities even within families. One child will be studious and another will not be. One child will be even-tempered and another will anger quickly. These things (to say nothing of the different talents that people have), make it clear that nature plays some role in determining our behavior.
For this reason, I do not agree with the view that the process of socialization explains all of our behaviors as human beings.