I've seen a few times people cite Furr while disavowing him in a more general sense, but I have never seen someone here talk about specific problems with him and his work.

I remembered this fact because I was looking up information on Losurdo and found a little eulogy Furr wrote for him (which incidentally had the answer I was looking for, that Losurdo did not speak Russian).

Furr seems like an absolute crank in terms of his general writing, see this text at the end of an article he wrote refuting a Current Affairs article:

I have been studying the allegations of crimes against Joseph Stalin for many years. My intention is to research every one of them.

When I began years ago I thought that it would be only a matter of time – perhaps a year or two – before I discovered that at least one of these allegations against Stalin was true, could be confirmed by primary-source evidence. I was wrong. So far, after several decades of searching, I have yet to evidence that Stalin committed even one crime, much less the myriad crimes that Trotsky, Khrushchev’s men, Gorbachev’s men, and academic researchers have confidently asserted.

I intend to keep looking. Perhaps some day I will discover at least one genuine crime by Stalin that I can truthfully say is supported by the best evidence we have. If and when I do, I will publish it and the evidence to support it.

Which is just a villain origin story, though again I must say that every refutation I have personally seen from Furr (though few in number) made sense.

So I ask again, what is actually wrong with him? Or has he merely inherited his own "Black Legend"?