Ok, that's fair.  I have no problem with wanting revenge on those who destroyed Jerusalem and took you captives, but why would a man of God wish such death on a baby?  What role did the babies play in Jerusalem's fate?  How could anyone happily smash a baby, an innocent baby (as they all are) against a rock? 

Numbers 31:¹⁷Now therefore kill every male among the little ones

This is from Matthew Henry's commentary:  (From:  http://www.htmlbible.com/)

Verse 13-18 - The sword of war should spare women and children; but the sword of justice should know no distinction, but that of guilty or not guilty. This war was the execution of a righteous sentence upon a guilty nation, in which the women were the worst criminals. The female children were spared, who, being brought up among the Israelites, would not tempt them to idolatry. The whole history shows the hatefulness of sin, and the guilt of tempting others; it teaches us to avoid all occasions of evil, and to give no quarter to inward lusts. The women and children were not kept for sinful purposes, but for slaves, a custom every where practiced in former times, as to captives. In the course of providence, when famine and plagues visit a nation for sin, children suffer in the common calamity. In this case parents are punished in their children; and for children dying before actual sin, full provision is made as to their eternal happiness, by the mercy of God in Christ.

First off, dying from the plague is nothing like dying by a sword.  When you die from a plague, you weaken, you get sick, you die.  When you die by a sword, you are terrorized, you watch everyone around massacred, you watch your parents and family die, then when your turn comes, it's not guaranteed you'll receive a quick death.  So these are not a common calamity.  I'd take the plague over death by a sword any day. 

secondly, where he states the parents are punished in their children, he clearly contradicts the Old Testament verse:

Ezekiel 19 Yet you say, ‘Why should not the son suffer for the iniquity of the father?’ When the son has done what is lawful and right, and has been careful to observe all my statutes, he shall surely live. ²⁰The person who sins shall die. A child shall not suffer for the iniquity of a parent, nor a parent suffer for the iniquity of a child; the righteousness of the righteous shall be his own, and the wickedness of the wicked shall be his own.

Matthew Henry says that the children, by dying before they sin, are awarded eternal happiness.  Well, how is that in anyway just?  God awarding those children because their parents were the  worst of sinners?  Couldn't the Jews take the children and raise them in a new environment? And what about the girls that were spared, what about their misery at losing their families.  How is it right that the male children enjoy eternal happiness while the females are enslaved.

Finally, for his statement about the virgins not being kept for sinful purposes, that seems to be just an unsupported assumption.  So, basically here is a command from God ordering the massacre of children for the sole reason that their parents were sinners.  As for 'all the young girls who have not known a man by sleeping with him, keep alive for yourselves.'  

 

2 Kings 2:²³And he went up from thence unto Bethel: and as he was going up by the way, there came forth little children out of the city, and mocked him, and said unto him, Go up, thou bald head; go up, thou bald head.  ²⁴And he turned back, and looked on them, and cursed them in the name of the LORD. And there came forth two she bears out of the wood, and tare forty and two children of them.

 

This one is self-explanatory.  A Prophet of God, Elisha (Note:  Muslims believe in biblical Prophets, but reject verses such as these.  Muslims believe that these verses have been corrupted.  see Jeremiah 8:8) can't handle being mocked by little children, so he curses them in God's name, and God responds by having two bears tare the 42 children to shreds.  Keep in mind that while this is the Old Testament, according to Christianity, it is still the same trinity God of the New Testament (or more like the trinity God concept that the Council of Nicaea borrowed from Zoroaster, Philo, Swedenborg, Buddha, Hermes, the Qabbalah, etc.,  It does not exist in the New Testament, or for that matter, the entire Bible. )

Ezekiel 9:⁶Slay utterly old and young, both maids, and little children,

God kills all the sinners.  Everyone who has not been marked is slaughtered.  This includes the old, the young, and the children, male and female alike.  My question is this, how is a child a sinner?  Yet according to the old testament, little children can be sinners.

Hosea 9:¹⁶Ephraim is smitten, their root is dried up, they shall bear no fruit: yea, though they bring forth, yet will I slay even the beloved fruit of their womb.

A Prophet of God shows his hate for an entire people and their sinning ways, which, isn't that bad.  But when he says he's going to 'slay even the beloved fruit of their womb' it becomes a problem.   How could a baby that's yet to be born be guilty of anything, especially to an extent of deserving a death sentence?