As long as we are talking about skeptics and their questions about our faith, one that I recently heard was a common one: "If Herod really did kill all those innocent children as in Matthew 2:16-18, why doesn't history record it?"
Speaking purely philosophically, this is a pretty weak argument from silence: it assumes that (a) every horrible act from that period was recorded, (b) those records have survived to today, and (c) we have found and understood all relevant records which survived. If either of those is not true, then we we would not expect to have any records of the event.
Additionally, the records we do have of Herod the Great's history certainly does not make it implausible: he was described by historians as, "a madman who murdered his own family," and "prepared to commit any crime to gratify his unbounded ambition." He banished his first wife and child when a more politically-expedient opportunity arose; he used secret police to monitor the Jewish people; he prohibited and arrested any public protesters; he levied massive taxes to build lavish palaces and temples; he built many pagan temples, to the anger of his Jewish people; he put a golden eagle idol inside the Jewish Temple; he drowned his brother-in-law at a party out of anger; he tried to kill his second wife and when she withheld sex as a result, he tried her for adultery and executed her; he executed another brother in law; and he executed three of his old sons.
So yes, if he felt that there was a potential king being born in a small village in his kingdom, it is absolutely in his character to kill all potentials.
How many innocents?
The next obvious question is, "How many innocents were slaughtered?" The Bible doesn't tell us directly, it simply records that it is every male under the age of 2. Luckily, we have some good information from history which can help us.
Some preachers have fancifully said that this was thousands (or even tens of thousands of children), but archaeology shows us that was patently false. First-century Bethlehem's population was between 300-1000 in total at the time--so obviously, the "male under two" population was considerably smaller than this.
Looking at population demographics in similar modern countries to ancient Israel, we should probably expect that the population under two years of age was around 2-4% of the population. Therefore, the population of males under two was about 1-2% of the total population. (In Rome the population would have probably been more male-heavy than a 50/50 split; however, Jews did not practice abortion or infanticide, so we should expect about half of the 2-4% under two population to be male.)
So, where does that leave us?
Well, if the total population is 300-1000, then we would expect the male-under-two population to be no less than 3, and no more than 20 children.
This is not to minimize a horrible situation: try and imagine an entire village losing all of their infants in a murderous rampage by soldiers, while you are helpless and unarmed to make a difference--and even if you protested it or told anyone, you would be jailed. Herod was evil, no question about that. And this rural village was so small that everyone knew everyone--not a person would have been unaffected.
But it is also quite conceivable that the murder of 3-20 innocents in a rural village of a madman's regime would be lost to history, isn't it? Even today, in our modern age of Twitter and Instagram, it would not at all be surprising to find out that 3-20 children were killed in some Rwandan village or Pakistani village and the paper trail is insufficient to be discovered 2,000 years from now. So the argument from silence on the Massacre of the Innocents is very, very weak.
For this reason, I have always considered this argument particularly weak. It simply does not stand to reason that we should ignore the Biblical record in this scenario, just because the one or two historians of that period whose writings we still possess did not record this event in a rural village on the edge of the Empire.
A tangential point--the modern Massacre of Innocents
Matthew found the event hideous. To the early Jews and Christians, it was stomach-churning: so much so that Matthew recorded it even though it really didn't have that much to do with the actual story he was telling. Matthew invokes the image of a mother weeping for her children to bring it home for the reader.
The early Christians and Jews were outspokenly against abortion and infanticide. (Abortion is not a modern practice invented after Roe v Wade: abortion medicines were known, and infanticide was also common--either by leaving the children exposed in the wilderness or by spreading heroin on the mother's nipple to cause an overdose.) They interpreted Scripture the same way that we do, and know that every child is a human with inherent value.
Here we see Matthew mourning greatly the loss of less than 20 children. He found it so horrible that he put it in the Bible.
Today in America, over 3,000 children will be aborted. Over 56 million children have been aborted since Roe v. Wade.
Let's think about that:
Massacre of the Innocents: 20
Modern-Day American Abortions: 56,542,336
Let me put it this way: picture every person alive when Matthew was writing his Gospel--everyone in Israel and Rome and Britain and China, the ancient Indians and Native Americans, everyone. All of those added together were six times less than the number of worldwide abortions since I was born in 1980.
I am young, yet during my lifetime we have seen more children killed than lived in the entire world of the New Testament--times six.
This is our Massacre of the Innocents. And many people are just numb to it. I, for one, am sickened.