The argument about the death of David's infant son in judgment:
...instead of punishing the offenders, [God] chose instead to punish the child conceived during their adulterous relationship. "(B)ecause by this deed you have given great occasion to the enemies of Yahweh to blaspheme," Nathan said to David, "the child also who is born to you shall surely die" (2 Sam. 12:14). So David and Bathsheba had violated a divine law that decreed death, but rather than killing either David or Bathsheba, Yahweh chose instead to kill their child. We will admit that such a punishment would have inflicted considerable grief on David and Bathsheba, but that is beside the point. They were the ones who had violated Yahweh's law, but an innocent baby was the one who paid with his life for an offense committed by others.
I very much doubt that this writer is concerned about "an innocent baby," but let's frame the matter in larger terms.
First, we should note fairly that the phrase regarding "enemies" is likely a later insertion; it is evidenced only in the Masoretic text. Nevertheless, David was king, and set an example for his nation. A visible judgment was required to set against any idea that others could blithely follow in David's steps in sinning.
We can hear the objection at once: "Who cares? Is God an egotist?" No, God is holy, and God is concerned that the greatest number of people will come to Him for their eternal salvation. Skeptics who tend to think only of the moment have no conception of the out working ripple effect of individual actions (or inaction). If having no effect at all meant that thousands who otherwise would have come to God and found eternal life instead went to eternal condemnation, is that worth the physical (not eternal) life of one person?
For Christians this is an easy answer: The death of one man paid for the salvation of billions. Visible judgment upon a very public offense as the means to accomplish the same, though to a lesser extent.
-JPH