You were right to leave, the nurse in your case was totally out of line.
In regards to pediatric patients, the hospital does have the right to detain, especially when policies and procedures are being broken. The hospital has the duty to the infant, because the infant is not an adult who can make their own decisions.
A hospital can get sued if they discharge a pediatric patient to an unsafe home situation.
Nobody has taken into account that this baby was still in the hospital after three days. Was the baby being kept in the hospital for this long or was it the mother who wasn’t discharged.
The possibilities exist that the baby had medical issues, the mother had medical issues, or possibly the staff was reluctant to discharge this mother/baby out of concern for the environment to which they were being returned.
The ease with which this man kicked a female in the groin makes me wonder if there are physical abuse issues.