The very definition of anecdotal evidence and why it's unreliable hearsay.I don't know what you experienced, but I saw this and still see it to this day. I knew a lot of Dominicans that would not say, "I'm not black, I'm Hispanic". Now if you ask them about their white side they would be more than happy to elaborate. I knew a Dominican chick last semester who is clearly black, and has the body of a black woman. Anyways she would always say that she is not black, but Dominican. At the same time she would be quick to let you know of her Russian ancestry.
Now if someone here said "I don't know what you experienced, but I knew a lot of black people who would say I'm not black, I'm Native American...." the entire site would rightly call bullshyt on the legitimacy of that comment.