How can Jesus, be referred to as "A God?" (non-JW's)?

This scriptural "add-on" has caused much greif in the Christian community. Why was it coined? Where did this insertion originate? If Jesus and the Father are truly "one", and there is only "one" God, how can He be referred to as a "God"? This translation was, I believe, produced to separate the Father and Son, in order to gain control over mankind...What do YOU think? Please, No JW's