"Widely discredited" does not necessarily mean "did not happen". 

In this case, it means that the commission strayed so far from internationally accepted jurisprudence that its rulings can be considered invalid.

What does that mean? Well, for example, the commission allowed confessions achieved via internationally accepted definitions of torture to be used as primary evidence against the accused.

No civilian or general military court in any UN country would allow the same, for many good reasons to do with human rights, the validity of such confessions, and etc.

This and its other failures of justice discredited the commission. If we decide to take its rulings at face value, we're taking several steps toward a North Korean-style justice system.