Some terms, like beauty, are hard to define. To some extent the concept of justice would fall into that category. However, in my opinion, the concept of justice always carries the qualities of equality and consistency. Yet when the church describes for us the justice of God it is so obviously unequal and inconsistent.
Then the church attempts to explain their strange concept of God's justice by saying that God's justice is unquestionable because He is holy, righteous, and unfathomable to the human mind and reasoning. In other words, He operates under some other definition of justice which we humans cannot understand but must simply accept.
Again, to some extent the idea of an incomprehensible God is common to us all. The answers to many eternal questions elude us, leaving us to contemplate how God operates on many levels. In these instances, we are forced to accept mystery as simply the way it is.
However, since the subject of the Bible is largely ethical and is directed at man in man's language, it seems exceedingly strange that God cannot explain His own ethics to us in terms we can comprehend. I think the problem is most likely that the church has never understood God and the Bible account; and, therefore, they teach mystery when muddled theology is a better explanation.