I could say that the fact that Sweezy pretended that he had been enlightened on matters of technical economics by reading that notable work of J.V. Stalin, _Economic Problems of Socialism_ is a historical fact.
I could say that I approach this historical fact in a value-neutral manner: I make no evaluative judgment of it, and that I in fact ask for possible judgments and responses without including any moral-evaluation words in my description of this historical fact (for "genocidal tyrant" is a factual and value-neutral description of J.V. Stalin).
You, however, clearly do make an evaluative judgment--a strongly negative one. If you did not strongly believe that Sweezy had done something criminal and contemptible in pretending to receive instruction in matters of technical economics from J.V. Stalin, you would not be upset.
The cruelty is yours as much as mine. And the true, primary cruelty is Sweezy's, for doing something that you regard to be criminal and contemptible.
"De mortuus nil nisi bonum" applies as little to Paul Sweezy as it does to Richard Nixon or Joe McCarthy or Paul De Man.
"Do not forgive, for truly it is not in your power to forgive In the name of those who were betrayed at dawn."
--Zbigniew Herbert
Yours,
Brad DeLong