I don't know the person. I have nothing on which to base that 'faith'. So yes, if I see someone I don't know making claims that two different cameras or chocolate bars or cars or whatever, are the best I'm going to regard those statements as suspect.
I'm also reminded of an adage, not sure I'll get it exactly right: When everything is excellent, mediocrity becomes the standard.
Come on...."everything"...
Did he include a 50D and D7000 in the mix. He sequentially reviewed current, top of the line cameras. The first one was the best he had seen....until he saw the next one. Seems quite simple.
It was his opinion....based on whatever criteria he used.
It is easy to stand by the wayside and throw doubts....as you have done....but really serves no value but to inflame.
If you want to have something to saw, go out and do your own, independent test. Then, and only then should you voice an opinion....based n fact, not maliciousness.
I have not tested either the D800 or 1DX. I have tested the 5D3 and can compare it to he 5D2, 5D, 7D, etc., but that would not permit me to voice my opinion if the 5d3 compared....I could just say I am happy and satisfied itch it.