The interviewer asked me why I was so confident. And why I had the nerve to want to dig into the terms of the job (salary, growth opportunities and the like - I was a late stage candidate).
Full disclosure - I can't think of a time where I have been perceived as arrogant at all. I am generally well-liked and personable.
The interviewer seemed to have some sort of implicit bias - I think she really didn't think that black people should be confident in a professional environment. I can't imagine that she would have taken similar offense to a white guy asking those sorts of questions.