everyone is a product of his/her environment. If you believe this than everyone has a 100% valid excuse for EVERY bad thing that they have ever done. Even your brain is a product of your environment in the sense that the environment determined which sperm would connect with which egg =P.
its not an excuse. its the truth. if your abused as a child you may become an abuser or you may become a protector. its not as simple as your environment or who you are as a person. its a combination of a bunch of things.