The Holocaust is a lesson for humanity that is instructive on both a micro (personal) and macro (social) level. The idea that prejudice and stereotyping can be used by a government to create a culture of genocide is one message that can be ascertained from this period in history, but it requires awareness and activism on the part of individuals to fight the effects of propaganda. The Holocaust shows that bystanders share an equal level of guilt as the perpetrators. In turn, when prejudice, discrimination, and persecution takes place on an individual level, it is up to the citizens of a vibrant democracy to counteract these trends on both a personal and political level.
To me the ultimate lesson of the Holocaust is a historical maxim (truth): when a government is given absolute power of life and death over its citizens, with no legal or social framework to protect them, then genocide is going to occur. Every time, eventually, this has been historically true.
So it offers us a lesson for all governments. All governments need independent judicial branches, and guaranteed civil liberties. Even that is sometimes not enough, but because of the horrible and infamous example of the Holocaust, we know what to look for.
There are many lessons to be learned from the Holocaust. One of those lessons is tolerance. People who were persecuted were mostly Jewish but other groups were targeted as well. These people were targeted based on sexual orientation, mental and physical handicaps, and political affiliations - just to name a few. The Nazi's were not tolerant of these people at all. They refused to accept them and wanted them extinguished because they did not fit in to their view of the "ideal" race. Because of this, millions of people were tortured and perished. The lesson learned here is that people need to be more tolerant, even if they are different.
The lesson and power of heterogeneity in our social orders and thinking processes prove to be the lasting lesson in the Holocaust. The naive craving for unity and symmetry helped to create a domain where individuals were willing to accept the most horrendous version of "the noble lie" as opposed to embracing the complexities and nuances of diversity and ethnic differences. The elements of social tolerance were abdicated for a supposedly "pure" notion of reality. The Holocaust instructs all of its students as to what happens when a society falls silent in failing to protect its diverse and heterogeneous nature. As a result of the Holocaust, individual students learn how powerful it is to live with difference and accept tolerance in all of its forms.
I think that the main lesson that the Holocaust should teach us is that we must not be complacent when governments start to treat groups within their country badly.
I think one of the major reasons that the Holocaust was able to happen is that other governments did not really care wha the Germans were doing to Jews before WWII. It was partly anti-Semitism, I think. It was also partly that no one could have imagined that the anti-Jewish laws would lead to mass murder.
So I think what we need to learn is that we can't say "oh, that's bad, but surely nothing more will come of it." We have to be aware that small steps towards oppression can lead to unimaginably horrible atrocities.
To not have Genocide on anyone; to not Have Ant-Semitism towards anyone, also to respect peoples Religious freedoms