A motif: A disturbing, atrocious motif

While doing some research on Isaiah "Teat" Dorman (The only black man to die at Custer's Last Stand) and Inkpaduta I came across something I keep seeing coming up when someone describes an enemy they want to make sure we, the reader, know is a vile and horrible enemy or that something is truly terrible.

• Inkpaduta is said to have dashed a baby's head out by holding the baby by the ankles and swinging it like a bat. Not all the sources say this is the case, the one I'm linking to, for example, doesn't say HOW the baby's head was dashed in with the stove wood.
• The Cankiri Tree was made by the  Khmer Rouge in Cambodia specifically for the soldiers to do the same thing to babies and small children of their opponents.
• I've heard, but can't find it online, where the Mongols were supposed to have done this as well during their rampage across Asia and Europe.
• Psalm 137:9 even mentions it: Happy is the one who seizes your infants and dashes them against the rocks

Why am I mentioning it? Well, it's a thing when researching something historic where the accounts are all anecdotal, from letters, from stories told by people instead of pictures or video, to be aware of. If you hear something once, at one place, it may be a thing. But when you hear it over and over again... maybe it's a thing. Maybe it's real, but maybe you need to dig a little bit and make sure you're not just reading something that sounds good.

Where does this fall in that for my Inkpaduta & Isaiah Dorman research? Well, I can't find a reliable source I'm willing to hang my hat on with it so I'm leaving it out. Everybody agrees the baby was beaten to death, but since most of those beat to death in the head were done so with the butt of a rifle it's just as likely that was what happened. Possibly while the infant was laying on the pile of stove wood. I'm not willing to say he swung the kid like a baseball bat.