Yes. Herod the 'Great' was a pretty brutal SOB by the time of his death. It is said that, knowing that he was hated by one and all, he had over one hundred members of the leading families (I believe this was in Hebron) imprisoned when he was nearing his death with the instructions that they should be killed when he died so that there would be mourning (and not just celebrations) when he died. Fortunately his minions did not follow his instructions. I presume they just had a 'ding-dong the witch is dead' hoe-down.
Slaughtering innocent infants certainly would've fit Herod's M.O.
Good analysis. I totally agree. Such an act would have been unlikely by David.