Why did they make such a big deal about "ethics" ?

The treatment of human subjects in research is a major consideration. In Milgram's experiments, he clearly put the subjects under a substantial amount of stress, as evidenced in their verbal and nonverbal behavior responses. He may have believed in the importance of it, and as this movie describes, his ego may have played into it, but he was not forthcoming with the subjects about the possible effects of the research. Whatever the case, he drew conclusions that basically described the conformists as potential Nazis capable of killing others based on their obedience to authority. I don't know if the bit about calling the subjects back for "debriefing" was true, but that could further cause them stress if their anonymity was not safeguarded in such a way that they could not be identified with their individual results, an important consideration in research which can be disturbing. Regarding the "1%" that reported dissatisfaction, if that number is valid it's a pretty impressively low rate.

Those professors/deans whom he discussed in a room, one said that research and science should aim for good, not bad as it was in this experiment. So basically most academics didn't want to accept that not every Nazi wasn't bad. So basically Nazis bad, Americans good, yet this research proved that Americans were willing to obey authorities more than subjects/subordinates. This thing hasn't changed and people still behave similar way even though the know or at least they should know about Milgram and Zimbardo. There was a case in Irak Abu Ghraib prison where Americans tortured prisoners(or didn't treate humanely), because they were told to do so and also told that those people are not equal/morally as good as them. So prisoner were treated bad, because leaders said so, co-workers did so, or it was believed that they aren't on same level as them, because they have killed American soldiers. There it was combination of Stanley Milgram, Louis Zimbardo and Solomon Asch. So social pressure, obedience and higher moral viewpoint.

And that Abu Ghraib isn't the only place. Similar higher morality, ethical superiority and group pressure happens everywhere every day, because in most cases it is easier way to do. It is easier to fit different kind of people in a group and be a part of another group than treat them as individuals and think individually. Yet people aren't stupid, but it is just a way to reduce own stress. So skinny people think that fat are lazier and they don't have disipline or Americans think they are better than Russians/North Korea, but they (might) think they're better than other group. And in most cases it is more difficult to learn about individuals thoughts, because there are so many, it is easier to believe leaders and be part of a group and let others be another group. In some case it is even harmful to think otherwise than group you're supposed to belong. North Koreans cannot express that America is better, because it is possible fatal to think otherwise. On the other hand working in a company A which manufactures phones to think that company B manufactures better phones. This case was partially harmful for Nokia, because they thought and were believed that their phone is better than iPhone. Even though individuals thought that iPhone might be a threat it was better to belong same group as boss and support that idea. So people on every level of company hierarchy had grown into company's extremely successful way of doing business. They had beaten Ericsson and Motorola who were their biggest rival. So they were used to those rewards they got from performing better than expected and didn't want to accept thought that someone else could be better. This same hive mind caused 2007 subprime crisis. People might have thought that something is wrong, but it was better to be part of winning side and even though they were sure that *beep* will hit the fan, they wanted to stay in that train and not go to the opposite side, because they didn't personally know anyone who might get hurt if things go wrong. An it basically pays to be stupid and follow herd, earn money and secure own life than being smart and stay away from that kind of business. People lost their houses and government bailed many bank out. Those who lost their houses and were just lazy, black or some other group, because success was for everyone to reach.

So morally people want to be better than just animals and in this experiment showed that it isn't always the case and it was unethical to show that people aren't always above animal behaviour.

Some of the comments on this thread are suprisingly ignorant and the last one sociopathic.

The problem with the ethics of this experiment isnt "science should aim for good".. that's bizarre and made up. The point of science is to discover the truth. The Biggest ethics problem with this experiment is the use of deception on its subjects. While in some experiments telling the subjects the point of the experiment.. or even not telling them and risking them guessing and trying to sway it... deception has a Bigger risk of influencing the experiment. While psychologists still use deception it is generally avoided.. and btw thats one of the many reasons psychology isnt considered a "hard science".. ie it isnt a science for the most part. Another ethical problem with this experiment is that is designed to get a particular outcome rather than test potential outcomes.
There are several problems with this experiment (and similar with the stanford experiment. Some of them are: the subject pool... experiments which rely on college students as their base.. and usually elite/upperclass school students probably drastically effect the results. Do the same experiment on a group of ww2 combat vets or blue collar minorities youre likely to have a radically different result. The conditions: subjects know it's an experiment. Performed by peopel at a prestigious university by a prestigious professor.. they assume it is safe. They assume the shockees are willing volunteers. They KNOW if people are harmed the university gets sued and the experimenters go to prison.. this is america...
And so on and so on. So while most would agree this experiment displays that humans can be authoritarian it is deeply flawed.