There is also no question that there were gas chambers in the camps. The question is how the gas chambers were used.
The steel door of one Dachau
gas chamber made the cover of Life magazine. There is no question the gas chambers were real.
The real gas chambers were small, between 10 and 12 cubic meters, about the size of a very cramped bedroom. The small size was clearly not designed for the industrial extermination of millions of people. The historians don't tell you that.
The real gas chambers were sized just big enough to push in two
racks of clothes. They were used to regularly fumigate the clothes of camp internees to kill vermin (fleas, lice, and other bugs) that caused epidemics (typhus, dyssentery, cholera). Zyklon-B, specifically formulated as a fumigation insecticide, was used.

Dachau gas chambers in actual use during WW2.
The real gas chambers all had a small heating box with flow-through ventilation that held the Zyklon-B pellets. Zyklon-B was designed, as a safety measure, to release no gas at room temperature, so it had to be heated. The historians don't tell you that.
The concentration camps originally had no gas chambers. They were added to the camps in the first years of the war to stop the typhus epidemics that were sweeping the camps. That's also why hair was removed from internees. The lice that carry typhus live in your hair. Shaving heads and installing gas chambers were sanitation measures to maintain human health. And it worked. The historians don't tell you that.
When the Allies chose a deliberate policy of mass extermination of German non-combatants (women, children, and the elderly) via the bombing and incineration of German cities (an undeniable war crime of shocking magnitude), an unanticipated change occurred in the camps. Supplies (medicines, food, Zyklon-B) to the camps steadily decreased until they were no longer available. Camp internees, now without adequate food, began to waste away. Without Zyklon-B, fumigation of the clothes stopped, epidemics returned with a vengeance, and internees wasted away even faster through highly contagious and deadly disease. The bodies of the emaciated victims accumulated at a frightening pace, completely overwhelming the camps. There was not even fuel to run the crematoria, so highly contagious bodies could not be properly disposed of. It was the perfect storm, and the Jewish propaganda machine took advantage of it, inventing the Holocaust. The historians don't tell you that.
When the camps were liberated, Allied soldiers were shocked by what they found. Ignorantly assuming the German soldiers running the camps had caused these horrific conditions deliberately, they often
killed them as they surrendered, no questions asked. Despite being liberated, the death rate among internees in the camps continued unabated for weeks until DDT was brought in to disinfect them and kill the lice. Yes, the dangerous DDT was
directly applied to the bodies of the internees to do the job that the Zyklon-B had once done to their clothes, but the DDT was necessary to save their lives, exactly as the Zyklon-B had been. The historians don't tell you that, either.
It's not that we can't handle the truth. It's that they can't handle us if we know the truth.