Atigun the Devil's Advocate. Seems you're something.
Not all people killed in the concentration camps were Jews. Some were Germans that rebelled against the Nazis. Some were gypsies. Some were political enemies within Hitler's government. Some were POWs. Some were Jehovah's Witness. Some were Seventh Day Adventists. I guess all these groups are lying too.
Not all people were burned. Of the 6 million Jews killed by the Germans, some were shot and buried in mass graves. Some were experimented with by doctors and many were gassed and burned. We literally overran concentration camp after concentration camp as we destroyed this EVIL EMPIRE. We found and chronicled the discoveries that lay smoking in the ovens. We found the warehouses full of teeth, clothing, hair, and all other personal effects. We found the half-dead people. We found the open pits with the bodies decomposing. You can't make this stuff up, just like we can't make up the Cambodian killing fields, or the Iraqi torture cells, or the Japanese atrocities in Nanking/Burma/Korea/Manchuria/and the Phillppines.
Some of my closest friends lost family to Hitler's concentration camps while others lost family to Hitler's war machine, whether they were Jewish, Polish, Ukrainian, Russian, French, or whoever-it made no difference to the Germans. You think they lie about all those relatives dead? You think they made up stories of slavery, rape, torture, depravation, and the inhumanity from German hands? You think the gold, paintings, and real estate that once were held by all these people magically appeared in Nazi's hands as reward from Thor?
Finally, the Germans kept meticulous records, just as the Stazi (East German Intelligence), the Stalinists, the Kmer Rouge, and Saddam's regime kept meticulous records of their savage insanity.
Sadly Atigun, it is people like you that will enable dictators to do all again.
My own mother, now 83, was arrested for not joining the party and placed in a Krup work camp. (light security and she escaped). But she never found out what happened to her father after the war. (He worked in the coal mines and was a known communist.) So, thanks, for reminding everyone it wasn't just the Jews who were exterminated.
However, as far as denial, my aunt was a Nazi youth and denies to this day any of the atrocities were attributed to Hitler.
Many years ago, I talked had a Vet who was one of the first GIs to enter one of those camps. He was a real life tough guy --- a no nonsense steel worker who fought his way across France and Germany and saw all that combat could bring.
He couldn't even finish telling me the things he saw when he went into that camp. He just broke down crying and told me if I ever heard anyone saying it didn't happen to call tham a damn lier. He probably would have just punched them out on the spot -- maybe worse.