to try and put it succinctly:

the farther we get away from the times when these things happen, the easier it is for folks without that context to believe they are true

for lack of a better term it is a form of "recent-information bias"

if "Recency bias" is the phenomenon of a person most easily remembering something that has happened recently, compared to remembering something that may have occurred a while back.

then "recent-information bias" is the tendency to believe what you are hearing now (often the first thing) compared to looking at events through the lens of the times in which they occurred (or norms therein)

now in the case of Jackson, we are in a space where as a reaction to years of NOT believing victims (the "prove the crime too place" era) we are swinging the pendulum to the place where accusations are pretty much accepted as fact and the accused needs to prove their innocence so folks will see that documentary and react to the pain of it all with acceptance/belief rather than look for supporting facts

on a wider scale though I see a frequency of wanting to look at something from times past and judge it through today's lens (essentially asking: would THAT behavior be cool today? then passing judgement when the obvious answer of no results). This is initiated with ZERO consideration, or care really, for what might have precipitated or caused the incident in its time (for example this OP: http://board.okayplayer.com/okp.php?az=show_topic&forum=4&topic_id=13309604 )

it makes conversation difficult because folks get locked into a position and just wanna share and repeat it until folks either stop dissenting or accept the argument because of the level of passion therein - facts, logic, and reasoning be dammed

just a random thought/opinion