Should machine learning from crawled dark web content be banned?

I disagree, there are a lot of applications in IT forensics. I have seen a masters thesis about the analysis of instant messenger texts. To identify illegal material with ML this content is essential.

(in the same way that machine learning may exhibit unconscious bias based on the datasets it is trained on, I fear that dark psychological traits could potentially be learned from traumatic content)

How do you propose to enforce this? (for human or machine)