there isn't much left to learn from the milgram saga, other than that the consumer public absolutely loves pop-culture science.
https://www.sciencedaily.com/releases/2017/03/170314081558.h...
(And some might have thought that the whole thing was then a waste of their time anyway?)
Those rules are of course another example of obeying authorities :)
If you're referring to the fact that the experimenters had to lie to the subjects and deceive them, not just in one individual statement but over the whole experimental scenario, the reason why that's not a good idea is actual practical, not ethical: constructing a false scenario and properly controlling what the subjects believe in a false scenario is very hard.
For example, consider this post by The Last Psychiatrist:
https://thelastpsychiatrist.com/2008/05/first_person_account...
The key point is here:
"He didn't stop because of moral courage; he stopped because he thought he was being played."
In other words, he figured out that it was a false scenario and his refusal was based on that, not on any moral objection to shocking people. But he got counted as a "refusal". How many other people who didn't refuse had some intuitive sense that the whole thing was a setup, thereby dampening whatever moral impulses they had? There's no way of knowing. The fact that it was a setup changes the whole experiment, as compared to one where all of the information being given to the subjects is truthful.