We all know the saying "the road to hell is paved with good intentions."
But nothing demonstrates its meaning quite like an IRL example.
They serve as cautionary tales.
A man named Dr. Spock wrote a handbook for childrearing. It was widely circulated and well received. Many of our parents likely got their childrearing advice from this book.
In it, he recognized that babies throw up a lot and therefore recommended newborns be laid on their stomachs to sleep. Unknowingly, this would result in the accidental smothering deaths of thousands of newborns.
A huge number of SIDS (sudden infant death syndrome) cases can be laid at his feet.
To this day the back-to-sleep campaign is still fighting to update parents on what we now know: newborns should sleep on their backs until they can reliably roll over for themselves.