I think that can depend on how you feel about your family. One of the most validating things I ever heard was that my family had issues... my wife on the other hand, would have a really difficult time hearing anything that is not totally positive about her family, but her family isn't as screwed up as mine. It sounds like the op was validated when t acknowledged that her family members are tough to live with based on how they were being spoken about.
Just curious, what makes it unprofessional to say in your opinion? Would it be that t has not met said family members? Or that t is overstepping bounds by talking about others? Or something else? (Genuine curiosity)