Here are four reasons why this is bullshit.
1. Not everyone killed by the Nazis had their bodies burned. Up to 40% of the Jews murdered by the Nazi government were killed in mass shootings and buried. There were multiple mass graves containing hundreds of thousands of people shot and buried by members of the Einsatzgruppen.
2. Of the corpses that were burned, not all of them were burned in ovens. Eventually, as the tides of war turned and the pace of the murders was ramped up, they threw bodies into flaming pits and used human fat from the dead as an accelerant.
3. Stacking bodies into ovens and turning them up to full blast doesn't require the same care or patience as baking bread, especially not when your objective is to cremate them quickly. Bodies were thrown onto remnants of bones and remains were burned again and again until (roughly once a week, at least at first) the ashes were removed and tossed into a river. So this whole comparison was asinine to begin with.
4. The ovens used in the death camps weren't standard crematoria. They were more similar to garbage incinerators. These ovens could incinerate up to 120 bodies over a period of 24 hours. They used coke, natural gas or fuel oil to fire these furnaces, and they recycled the waste heat from the hot exhaust gasses back into the system. After the cycle ran for a good few hours, the burning tissue and body fat delivered enough energy to keep the fire running as long as you fed new bodies into it without having to supply additional fossil fuels.
So yeah, Holocaust denial is bullshit and anyone who seriously entertains the notion that the most well-documented genocide in history was an elaborate hoax is either in desperate need of an education or a rabid anti-Semite.