I do agree that it was rude for the attendant to speak about you in that way.
I worked for an airline for many years and though it may seem like a good idea to take a pup out of his carrier or to open the carrier to give him a break, I totally understand why they want them to remain in a closed carrier under the seat at all times. Not only are the rules there for the passenger's safety, but they are there for the pup's safety as well. It's not unheard of for an aircraft to suddenly drop a couple of hundred feet or experience sudden turbulance. Most times the pilots are able to predict these things and request that passengers buckle up, but there are times when it happens unexpectedly (that's why I never take my seatbelt off...only to go to the washroom
) A pet out of his carrier (or even if the carrier is out from under the seat) could get severely injured.
I do understand your frustration with the attendant...she was rude and that is uncalled for.
Check the airline's website. If it's the one I'm thinking of, they have all the info there regarding travelling with your pet.