I think the whole training and such AI was just bad designed. Aren't all first impression judgements prejudices as much as all racist bias are? If I say a person is attractive, inspires me just based on their looking it is a positive judgement, a bias based on the looks and a few traits I subconsciously perceive and perhaps I cannot even explain, and the same with the negative ones, and I guess for some people this association happens also to race and looks. Basically an AI was trained to map the prejudices of their inputs, and that means to create a snapshot of the subconscious average of whoever behind the mechanical turk is, everyone has prejudices of all sorts which usually are not manifested externally but in a process of classification such as the one of the mechnical turk might arise much more.