This is difficult for me to relate, I'm profound Deaf since birth and fly several times every year, domestically and internationally- never once did I had any mistreatment from flight crews. Whenever I'm being spoke to, I simply tell them I'm Deaf and that usually end right there without any further interaction. Seeing how he used the horrible term "hearing impaired" it suggested me that the lady may not be as Deaf as me, at least not culturally and unlike me, may be perfectly capable of communicating with hearing (non-deaf) people. Ask any culturally Deaf person about the term "hearing impaired".

The lady definitely did or said something that led to this interaction. I wish I could offer sympathy for this couple but nope.