well, they hang it, raw, for two weeks (in our case) that is sort of rotting it, right? if you listen to kevin trudeau etc they say that's terrible for you. but it's SO much more tender.
Hanging meat is *extremely* traditional, especially for game that can definitely be tough, especially if it had to be chased before it was killed (stress hormones can toughen meat). I can't see how it would be bad for you though. So many of the processes that unlock nutrients for all foods - fermentation, soaking, etc. - are controlled rot; hanging meat is no different, and CERTAINLY humans are adapted to eating less-than-fresh food, we'd have never survived prehistory or even the middle ages otherwise.