It seems like it would be easy to predict an individual's reaction to the thing by looking for correlated reactions between that and some other things from people who have seen it all, and then seeing how a given innocent reacts to those other things.

I bet some pretty strong patterns would emerge, and we could predict reactions to the thing. I do not think that protecting people from harm now is a true objection, for it could be dealt with by identifying vulnerable people and not making the whole topic such forbidden fruit.