Yes, luckily, psychological experiments are much more regulated now!
I can say I'm an expert, but it seems to me that even the old, unethical ones did have some scientific value. I think that all three mentioned experiments at least did confirm presumptions about situational depersonalization, obedience to authority, and conditioned fear. Of course, the methodology was far (FAR) from perfect, making the results hardly measurable.
I agree with you that the experiment on social isolation performed on monkeys were, at least, as cruel as the above-mentioned three conducted on humans. :/