Milgram's "Obedience" and the Stanford Prison Experiment are less examples of some underlying human nature, and more examples of how we are socialized to view authority and indoctrinated into tribalism. Yes, they demonstrate a "nature" of humanity as it currently exists in western civilzation. However, there is nothing shown by either of these experiments that proves that this is innate and inborn. If we chose, we could just as easily raise our children to not fall in line with these models of authority and interaction, and the various cultures around the world and throughout history who do not comform to these examples (and even the statistical outliers in Milgram's work) are all the evidence required to demonstrate that this is possible. We can easily be better than the subjects of these two experiments, assuming of course we're willing as a people to change our own culture, which despite cynical pronouncements to the contrary, is something that's happening anyway as an ongoing process; you can't tell me with a straight face that our understanding of human rights and dignity (as imperfect as it is!) is not superior to that in, say, Victorian times, or during the Roman Empire? Culture is an everchanging and ongoing force, and we can talk about whether it advances at some times or regressess at others, but if anything is proven by all of this, it's that nothing is innate in human nature, except perhaps "Dunbar's Number".
So no, I reject the contention that we cannot improve our world and society because "humans will be humans". Culture is already changing, every day. Folks like Desp are trying to nudge it in specific ways to get to specific destinations a little faster, sometimes successfully, often not. However, I respect that far more than just taking the lazy way out and making cynical appeals to "human nature".