What would you say to someone who looks you in the eye and says "the holocaust is a hoax"

I would say that denying the Holocaust is not only historically inaccurate and deeply offensive, but it is also dangerous. The Holocaust was a real and tragic event that resulted in the senseless deaths of six million Jewish people and millions of others. Denying or minimizing the Holocaust is a form of Holocaust denial, which seeks to erase or downplay the atrocities committed and perpetuate hateful ideologies. It is important to educate ourselves and others about the reality of the Holocaust in order to prevent such atrocities from happening again.