Why Do Some Non-Christians And Christians Quote The Old Testament While Ignoring The New Testament ?

The old testament is a little more violent, a little more God as a thrown down lightening and thunder when we mess up. While in the New testament, Jesus shows the God is a forgiving God who loves us even when we make mistakes. Thus to those who want to besmirch Christianity it is easier to show the "EVIL CHRISTIANS" by just using the old testament.