I wasnt offended he "asked" me about being mixed. Im not biracial. I have Choctaw blood but it was my great great grandmother. To be honest what person is 100 anything if their family has been in the US a long time. I choose to identify as black. I was offended that i told him Im black and he insisted Im not which I think is disrespectful. I dont think being taken for mixed or for black is an insult. However, Just like if you told me you're mixed and I argued with you that you were just black that would be wrong.
BTW i went to Africa a few years ago and saw lots of people my complexion.