The moralities of society do indeed change, but the rules of the time and the prevailing social consciousness do still affect our interpretations at different times. The lack of drug rules (and poor general understanding of drugs at the time) leads us to vindicate Thomas Hicks. The presence of drug rules (and increasing societal disparagement of drug usage in sport) leads us to vilify Ben Johnson.
As much as I understand those who vilified him, I think it is probably about time we dropped the "Big Bad Ben" outlook. It is a very shallow one which purposefully does not seek to place him beside his peers. In Johnson's BBC interview 18 months ago, I found myself in frequent agreement when he was describing his competitors and peers.
Where he still falls down is in his self perception - I remember in his interview he said that his peers were cheating, but that he was not cheating because he intended to "level the playing field". These are incompatible views. All these years, he has failed to say the real situation: many of his peers were cheating, just as he was alongside them. This is a less morally repugnant reality than the one we are often presented with.
In my view, it is not reasonable to award Johnson any medals, but it is desirable to understand the environment he competed in. Underneath all the scape-goating and hysteria lies a fascinating story of desire and human failing.