What to do about Hitler deniers?

What shall we do with growing number of people who believe Hitler was a hoax?

Hitler was an amateur painter, soldier, and political leader.  Hitler never wanted to kill the Jews. He wanted to deport them to Madagascar, and kept them in temporary living quarters filled with theaters, swimming pools and five star breakfasts, even when the rest of Germany was starving.  Unfortunately, the Jews used this as an opportunity to betray him by making false and outrageous claims about his hospitality.  Ask any historian: even today, we know Hitler never killed any Jews.