Is the God of the Bible immoral?

I have been listening to many atheist/Christian debates recently, and one thing I continue to find striking is the continual atheist insistence upon the immorality of the Triune God.

Atheists consistently point to the "immorality" of the Old Testament God. They will point to the conquering of Canaan and the allowance of evil in the world, etc. They also continue to point the immoral acts that Christians have committed in history such as the crusades, the inquisition, etc. (Which doesn't prove anything about the truth or falsehood of the Christian faith; rather it confirms the reality of human sin which the Scriptures testify to).

But in reality, if either the Christian position is correct or the atheist position is correct, the God of the Bible cannot possibly be immoral. Let me explain.

First, take the Christian position. If God exists, he is by nature the standard of moral absolutes. The moral law is a reflection of God's own nature. Since God is by definition the standard of good, anything God does or says is by definition good. Therefore, by definition, God cannot be immoral or do anything wrong or evil.

Second, take the atheist position. According to a purely materialist approach to reality, there is no absolute standard of morality. There are several attempts to identify some type of standard of morality such as the consensus of a certain social group, a utilitarian approach that the greatest good for the greatest number is a moral standard, etc. However one wants to slice it, there is no objective standard of morality inherent in the nature of reality. This being the case, there is no purely objective moral grounds to judge the God of Scripture as immoral. When one argues in such a way, they are arguing with the assumption of an objective moral standard, which is a human presupposition rather than something derived out of the atheistic system.

The only way that one can possibly argue that the God of the Bible is immoral is by admitting that there is another, higher, objective moral standard by which He might be judged. Thus it is possible for someone from another theistic system to argue for the immorality of the Biblical God (much like a Christian would argue for the immorality of the portrayal of Allah in the Quran), but not for the atheist. Of course this would lead to a whole separate discussion of the reliability of the respective authoritative books, etc.

The fact is that an atheist cannot argue for the immorality of the Biblical God without first presupposing an objective moral system, thus acknowledging some form of transcendence and absolute truth regarding morality. Thus one is inconsistent with their own system.