Agreed. It was literally documented by the perpetrators. What was for posterity now is evidence.
I'm totally open-minded on anything and everything. There is still (I believe I'm correct and this hasn't changed) nothing that explicitly ties Hitler to the actual Holocaust. No formal, written, order ever found. So if you want to argue that it was the brainchild of Heydrich and Himmler then I'll listen to the evidence.
But for someone like Irving to deny it happened. It's just someone being objectionable for the sake of objection. I lose my patience then with it.