It is hard to know why these guys are being so pigheaded. So one assumes it is the usual Kosher Nostra diktat from above.
There has been carbon dating of some of the mortar which proves that Khufu did not build them. Since you cannot build something for which some of the outer mortar was there 370 odd years before you were born. Paradoxically the numb-skulls take this as evidence for the Khufu thesis?????
A better explanation is to note that none of the dynasties had the tools to build these things. But there is a good possibility that the required technology was available prior to the quaternary extinction event.
Since you cannot build the great pyramids with copper or bronze tools, or with the tools of Cro-Magnon man (stone hammers and wood) that leaves two main options:
1. That an earlier dynasty than Khufu had the required hard tools for the job. But that we somehow have not picked up any evidence for the better tools.
2. That the pyramids were made far earlier, before or just after a major crisis that lead to a massive loss of technological capacity.
In the latter example the mortar presents no problem, since after thousands of years, rain damage would necessitate make-shift repairs to the outer facade. The mortar is a bit out of place in any case, since the inner pyramid is mostly made without mortar.
Never let a professional in any area abuse you with crimes against logic.