What are your thoughts regarding predisposition and pre-determination in human behavior?

This article by Chris Renzo argues that having a genetic predisposition for something does not mean that you are pre-determined to have or do said thing. Some scientists have indicated that social factors, the environment in which we are born and raised, can influence or determine which genes are expressed.
What are your thoughts on whether or not having a predisposition can, or is, used as a cop-out or justification for inaction and that it is society that is instrumental in breeding violence not genes?