For all we know, these are the kinds of people who, when approached on the street, said "sure, I'll go on The Death Show". They're the same kids who stomp on worms after it rains - a small minority of the complete population.
The main point of the original Milgram experiment was that you don't need much to get ordinary people to act unethically if you provide them with the proper context. Saying it's only a small part of the population that acts this way misses the point.
Showing that there are those among us who will gas women and children, and many more who will not do anything about it as long as it doesn't affect them personally is a repeated lesson of history, not some psychology study.