As there are no more arguments that there are holohoax mass graves, I'll suppose that the flack has conceded that point.
And due diligence suggests dealing with the hoax account of why there are no mass graves, and that is that they were all made to disappear by Paul Blobel, SS Commandant who did or did not command the Einsatzgruppen group responsible for the Babi Yar hoax, who was then relieved of his command due to alcholism, and finally given the assignment of removing all traces of Einsatzgruppen activities in eastern Europe.
So, what have we got to go on? Paul Blobel was tried at Nuremberg, not at the main trial but a subsequent trial, and I have not found a transcript online. However we do have two affidavits signed by Blobel.....
http://www.holocaustresearchproject.org/einsatz/blobeltest.html
On the subject of mass graves, Blobel states here ...
In the fall of 1942 I was assigned to go to the occupied Eastern Territories as Mueller’s deputy, and to wipe out the traces of the mass graves of people executed by the Einsatzgruppen. This was my task until summer of 1944.
After that....
The sheer idiocy of these 'confessions' is beyond belief. That's it folks, that's the evidence for the disappearance of a few million buried bodies.
Well, maybe we'll have better luck with the second affidavit ...
http://www.law.umkc.edu/faculty/projects/ftrials/nuremberg/affblobel.html
Here we learn ....
3. During my visits in August I myself observed the burning of bodies in a mass grave near Kiev. This grave was about 55 m. long, 3 m. wide and 2-1/2 m. deep. After the top had been removed the bodies were covered with inflammable material and ignited. It took about two days until the grave burned down to the bottom. I myself observed that the fire had glowed down to the bottom. After that the grave was filled in and the traces practically obliterated.
So that's how it was done !