@zuzak
Why must justice and mercy be mutually exclusive? Since you said "by definition", let's look at some definitions of just and mercy (from dictionary.com).
Just:
1. guided by truth, reason, justice, and fairness.
2. based on right; rightful; lawful.
Mercy:
1. compassionate or kindly forbearance shown toward an offender, an enemy, or other person in one's power; compassion, pity, or benevolence.
2. the discretionary power of a judge to pardon someone or to mitigate punishment, esp. to send to prison rather than invoke the death penalty.
God is just. In that he embodies truth, reason, fairness, etc. So man is judged, and the law is carried out. The law being that sin results in death. However, God also provided a way for the law to be fulfilled without our personal death. That is, Jesus Christ. Through his death, the penalty of the law was paid. In my mind, there is no way to be any more merciful to us than that... allowing another to die in our stead, God's own son. So the law is fulfilled (justice) and people are given a free gift of life (mercy).
Also, wow. There are a lot of loooong posts in this thread. I'm afraid I didn't read all of them. If I just echoed what someone else already said, sorry. :)