Using people can lead to 'harmful exclusion, discrimination'
At first I wondered why the 'big' in this report. After all they firstly talk about aggregated data...
Then I realised that what they really mean is that people are very good at ignoring the things they are taught about - especially being aware of, and avoiding, biases. There are whole book shelves on this stuff. There are even pop-science books on it (Thinking Fast and Slow springs to mind).
This isn't a problem with data, 'big' or otherwise, it's a problem with dumb people doing things in a dumb way, drawing dumb conclusions, and taking dumb actions. And then forgetting to monitor the outcomes. It applies to pretty much every form of human action since the first inference was drawn.