From the Wiki link"Milgram argued that the ethical criticism provoked by his experiments was because his findings were disturbing and revealed unwelcome truths about human nature"This experiment completely discredits the "humanist" idea that people are basically good and will "do the right thing" if given a choice thereby completely undermining the entire liberal philosophy as currently espoused.
I also wanted to mention that the National Holocaust Museum in DC is very powerful and more accessible. I went through it just after it opened and it was able to take the facts (that I already knew) and turn them into experiences that brought the reality home. I will never forget walking into a small room that was wallpapered in actual photos of the piles of hair, clothes and personal items stripped from the inmates before they were led to the showers. Being surrounded by a pile of hair 10 feet high made my guts clench.http://www.ushmm.org/museum/I came out of the museum committed to "Never Again" in my life even though I am not Jewish.