Actually, if you see your neighbour beating her child, but you don't believe the child is in imminent danger of dying, than what you should do is call 911 and try to defuse the situation by offering to help the neighbour. If you believe the child is going to suffer serious harm or death, and you stand by and do nothing... well, that's on your conscience, isn't it? And of course you'll have to deal with the social consequences afterward, too, since you will be partly to blame for whatever happens to that child.
However, in THIS case, calling 911 was not an option. The flight attendant, in an effort to keep the flight calm (her job), offered to hold the baby (ie. help the mother). She did not keep the baby - she gave it to the father!
She did absolutely the right thing, the legal thing, and I'm not sure on what basis you're continuing to argue about anything.
What to do if you witness child abuse
# Avoid physical confrontation
As upset as you might be from witnessing child abuse, do not confront the abuser. Alert others in the area whose job it is to handle the situation — such as management or security.
# Call 911
If the abuse is taking place at a location where there is no management or security, contact your local authorities.
# Ask the adult if he/she needs help
Offer to help if the adult can't control the situation at the moment. For example, if the parent is lashing out because his/her child has thrown store merchandise onto the floor, ask if you can help to pick it up.
# Get a description of the parent and child
# Write down the license number of the car
# Call your local family services office
Contact them with the physical descriptions and license number that you have written down. Alert them to the situation and let them know that somebody needs to look into it.
http://drphil.com/articles/article/239