It's almost a parenting right of passage.
You a sleep-deprived new mama (or even a seasoned parent of multiple kids), are walking down the street with your newborn/toddler/preschooler strapped into your fancy new stroller/crunchy sling/avant garde trendy carrier/walking with your down the street and some (possibly) well-meaning soul stops you on the street.
"Your baby should be wearing a hat because it's so hot/cold outside."
"That poor child's head looks like it's going to fall right off. You should support it better!"
"Aren't you standing a little too close to the crosswalk?"
Depending upon your level of moxy and/or hormones, your first instinct is to do one of the following: 1. Burst into tears 2. Offer a knee-jerk angry retort or 3. Nod and smile blankly.