I asume you're talking about White Wallenborn. His argument against -- the monority report -- is included in the www.monticello.org site for all the world to see.Mrs. Gordon-Reed's book was a work of non-fiction, it was Barbara Chase Riboud who wrote the fictionalized account of Sally Hemings.
The burden of proof is on the Hemings if we wish to secure a burial place for ourselves in the Monticello graveyard, but many of us do not wish that, so will dispense with going to court over the issue. It really isn't that important. Some will never be convinced of the relationship, and I respect that. Conversely, neither you or the scholars with many PH.d's between them indeed, will ever convince us it didn't happen.