concept of crimes against humanity trials

I am watching a BBC doc about the Nuremberg trials. It is overall propagandizing against the concept of trying crimes against humanity at all. Due to, as described, the british position: it'll just be another chance for the defendants to present their position to the world so better to hang them and be done with it.

Q: Agree/disagree with the above? Both in the specific instance, and in general.

It was the first, but not the last, such proceeding. What are we learning from subsequent?