It’s a three-letter glimpse into what motivated these scientists to write the paper; I think we can acknowledge it and move on without losing sight of scientific rigor.

Tt appears to be a pretty sound review of evidence, and then a discussion and conclusions section where the results of the review are interpreted and implications are discussed. Seeing "sad" appear in an abstract is sort of unusual. However in the discussion in the review the arguments about morality etc are a bit more sophisticated, but I reckon it isn't too odd to have a value claim on the implications of the review being unfortunate, since they have real implications for human wellbeing. If the same sentiment was couched in normal amounts of academic jargon, you would likely not have noticed.

There is no gain from rejecting different types of truth that don’t adhere to a single way of producing it.