The flip side is, many people are abusing the right to have a "service animal" on board.  You can buy the vest and throw a fit and probably win most of the time.  There needs to be a legit process to document people who really have this requirement, a philologist should at least sign off.  If you want to be mad at someone be mad at all the people abusing the rule that caused the flight attendant to even question this in the first place.