Assuming the accounting is correct, I think the guy was OK to end the interview politely (without throwing a fit or making grand statements) and leave.
It was also not surprising they were shocked and upset, but that in itself doesn't mean he should have refrained from ending the interview, or that he was unprofessional.
I have thought of walking out myself, I think most have.
For example one interview the manager presented a long monologue about how stupid he felt people from a certain well known outsourcing country were. It wasn't even so much that he was racist, it was that that his stories showed he was closed minded, judgmental and reactionary. I doubt these personality factors were limited to his opinions about national origin. I continued the interview and declined the subsequent offer, citing another better offer. The other offer was for less money but was a project I wanted to work on more, the diatribe wasn't really relevant and only would have been if the offers were similar or his was for more interesting work. I chose not to give him feedback about his rants because I wanted him to keep doing it so other candidates would have the same warning. Him not saying what he really thinks certainly isn't going to change his actual personality.
In other cases I see the interview to the end out of curiosity and to have a good story to tell, but also because you never really know what is going to happen without seeing it all the way through. I may find out more about their business, I may make some contacts talking to people there. Or maybe it is a wash out, but having flown across the country I am going to make it to the end of the day's interviews.
It was also not surprising they were shocked and upset, but that in itself doesn't mean he should have refrained from ending the interview, or that he was unprofessional.
I have thought of walking out myself, I think most have.
For example one interview the manager presented a long monologue about how stupid he felt people from a certain well known outsourcing country were. It wasn't even so much that he was racist, it was that that his stories showed he was closed minded, judgmental and reactionary. I doubt these personality factors were limited to his opinions about national origin. I continued the interview and declined the subsequent offer, citing another better offer. The other offer was for less money but was a project I wanted to work on more, the diatribe wasn't really relevant and only would have been if the offers were similar or his was for more interesting work. I chose not to give him feedback about his rants because I wanted him to keep doing it so other candidates would have the same warning. Him not saying what he really thinks certainly isn't going to change his actual personality.
In other cases I see the interview to the end out of curiosity and to have a good story to tell, but also because you never really know what is going to happen without seeing it all the way through. I may find out more about their business, I may make some contacts talking to people there. Or maybe it is a wash out, but having flown across the country I am going to make it to the end of the day's interviews.