The moral advancement you refer to is for the most part illusional. Minority groups remain discriminated against as fervently as always, only the the discrimination is much more systemic, rendering it less overt and detectable.
Furthermore, the progress you're referring to (I believe) is progress taking place within the US, not within the world. Take for example the treatment of women, gays, etc. in places such as the middle east. It has not improved, if anything it continues to get worse. While we're in the middle east, let's look at what else is happening here that may suggest we haven't advanced morally.. Senseless and needless killing of innocent people by the US (your supposed morally reformed poster-child), more senseless killing in the Israel/Palestine conflict, more still in Egypt and Libia.. and the list continues. I haven't even made it to India, China or Africa.
Also, let us not forget the atrocities of our not so distant past. The holocaust was 65 years ago, the Khmer Rouge more recent in the late 70s and more recent still the Rwandan genocide in 94, and I'll finish with 9/11. Historically speaking these events are frighteningly recent.
Wars, genocides and fascist regimes continue to plague our world. As long as this remains the case, I see no evidence to suggest that we have advanced morally.
