Social mores change over time. This adds a major complication when analysing past events. Also the data sets available to judge past events have to be weighed as to their impartiality. This creates another major problem when it comes to deriving accurate interpretation. Distortion inevitably exists in the written record yet history texts seem to gloss over this aspect in their mighty tomes. Polarity of views in the existing record also clouds rational judgement.
It would be nice if the outcome of research was presented as shades of grey rather than as black and white absolutes.

The argument about soupers makes an excellent example. It was presented as an all encompassing blight. Revolting though the practice may have been the Wiki article clarifies that perhaps it was more a case of hype than actuality in the majority of cases.