I've noticed a tactic used by exterminationists which is they have a select few 'celebrity holocaust survivors' that promote/give speeches about gas chambers and various stories . . .
I am not familiar with the work of exterminationists or even who they are and their methodology. It sounds like crap, if they rely on a few "stars" to form their views. OTOH, I do know how historians and other scholars of the Holocaust have worked and how they've established beyond doubt that the Third Reich carried out a genocide against European Jews.
Historians do not rely on a "celebrity survivors" or even survivors. They, instead, make use of whatever relevant evidence remains about the period and issues they study - in multiple forms, of various types and differing quality. They study and compare the evidence, evaluate it, and draw conclusions based on it. In general, their conclusions come from their analysis of multiple, independent, and cross correlated sources and pieces of evidence.
Earlier in this thread, we discussed the mass murders at Ponar in 1941. Like historians, we examined multiple diaries kept by witnesses and observers, court testimony, German police and civil administration documents and reports, demographic data, Wehrmacht and Einsatzgruppen records, physical studies of the site, memoirs, maps, newspapers, posters, etc. Like historians, we carefully cross checked pieces of evidence with pieces of evidence. We also noticed how deniers were constitutionally incapable of dealing with all this, focusing instead on a few random points they felt don't fit in.
As opposed to deniers and others with axes to grind, historians learn to interpret a range of sources and use different forms of evidence to interrogate other forms, relying not on smoking guns and supposedly easy answers. Deniers, with their black and white view of the world, have trouble grasping how historians work and prefer going a point at a time and looking for random anomalies, small discrepancies, and magic answers.
In the threads on Holocaust denial, those members citing historians - to make the point clear - have discussed or referenced a wide range of souces, including census reports, statistical analysis such as demographic, economic, etc.; trial affidavits, ranscripts, testimony, and judgments; newspaper and other such reports from the time; posters, handbills, announcements; meeting notes, conference proceedings, and the like; speeches; correspondence, telegrams, and so on; construction plans and records; official documents, military, government, business and other institutional records and reports, personnel records, etc.; financial records; laws and official proceedings, regulations, etc.; photographs and film footage; diaries and journals; eyewitness reports; physical evidence; memoirs and oral histories; contemporary investigations and trials; technical information, manuals, and so forth.
By learning from such sources, historians and even lowly members of this thread can sift out unreliable sources and witnesses - and problematical points of testimony - from what correlates and meshes well with the range of evidence concerning the Holocaust. What historians and lowly members of this thread (leaving aside deniers) do not do is focus on one form of evidence and a handful of celebrities or stars (we would not, for example, focus on a "star" like Wiesel to determine our conclusions about gas chambers at Birkenau, when Wiesel himself was held at Buna Werke, a number of km distant from Birkenau; rather, we would use, as noted, a range of evidence, prioritizing that which is closest in time and location to the events and actions being studied).
It would be good of you to identify these exterminationists to whom you refer. For my part, I will try to continue operating like a historian would. If the deniers on this thread would try doing so, I am sure our discussions would be improved, although I doubt we'd have any deniers left.