What do you think about the groups that don't believe the Holocaust happened?

It is my belief that many people allow themselves to be blinded based on what they chose to be the truth.  I had the bad experience while living in Germany to meet several German mothers at a park one day.  My children were playing and I was studying a book on the Holocaust for a class that I was taking at a German University.  One of the women stated to me,” You don't believe that rubbish, do you?"  I then explained to her that it had happened.  I told her I had even visited the camps.  I did not want her to know my parents were Holocaust survivors at the time.  The other woman proceeded to tell me how wonderful Hitler had been to the Germans and that he only had taken from the Jews what had belonged to the Germans but the Jews had been sent to other countries to live.  I was amazed that they truly believed this.

I have read about the leader of Iran and his statements, but I know that there is no changing the mind of an individual who refuses to see. 

 The truth is validated by public records, artifacts, and the many survivors who shared their stories about their family members and their own lives during the Holocaust.  People like my parents  (Holocaust survivors) spent years telling their stories in schools and teaching about the love of humanity in an effort to prevent further atrocities.  We can not change the way other people chose to think, we can only share what we know and the rest is up to them.