Actually, in my mind, it is the flight attendant at fault here, not the mother. I also don't think in my mind that I would ever give drugs to my 19 month old child just so that arrogant, hoity-toity people, don't get to spend every blissful second that they are aboard an aircraft, in complete silence. We live in a society where people are allowed to have as many children as they choose. Sometimes these parents need to take a child aboard an airline, for whatever reason. It is even possible that this mother needed to take this child for medical reasons, in which case the child could have been on medication that could have had a serious reaction with Xanax. I don't know if that was the case -- Neither did the flight atendant, nor do you. The mother is not at fault here! Sometimes kids cry. If they are your children, then do what you feel is necessary. If they are not yours, Get over it!
If that had been my child, the flight attendant would be in desparate need of cosmetic surgery right now!