We Evangelicals believe in Justification by Faith Alone. God accepts us because we believe, not because we work. Sometimes we get lulled into the idea that although this matters, it is not that important to God. Certainly he overlooks a little working for the sincere. In other words, he accept Christians that believe in the cross but reject justification by faith alone. This doctrine is important but not crucial.
In an age like ours, one which prizes itself on tolerance, these are fighting words.
Why such strong statements? First, justification by works is a "basic principle of this world" (Gal. 4:9). It is the element common to all false religions. It consigns millions to Hell. Those who seek to be justified by their own efforts actually reject Christ and his cross. In Paul's words, this belief system "severs us from Christ" (Gal 5:4). In other words, if I can work my way into salvation why do I need Jesus? I don't.
The truth is the opposite. Christ came because self-salvation is impossible. When I insist on working I am really saying to Christ, "I don't need your cross." I can do it on my own. For God, the gift of Christ was infinitely costly. It is apparent why he is not too happy with those who take this stance.