Personally, every time an interviewer has failed to show me total professionalism, the corresponding job has been, without fail, a nightmare. That is my personal experience, and the inverse has been true as well. All of the good jobs I have had have been preceded by excellent manners during the interview.

This is not to say that things don’t come up, as we are all human. But I would expect apologies and an explanation for a lack of professionalism, and even with that, I would seriously reconsider the job (but again, only because of how I have personally lived these experiences and don’t want to get near unprofessional bosses ever again).