In what way is pointing out that a document purportedly produced by communists was not produced by them “defending communists?”
What you are in essence claiming is that this list is “fake but accurate,” which may indeed be true.
But I think conservatism’s single most important basis is a respect for reality and the truth. We don’t make up stuff about our opponents, even if it is convenient.
I’ve similarly been accused of “defending” Mormons and Muslims when I point out that accusations against them are untrue.
Personally, I think there are plenty of entirely true things to criticize about Mormonism, Islam and Communism. Why should we stoop to making things up? Don’t people realize that one of the best ways to discredit your own position is to make an accusation that is easily proven false? It damages your credibility in making other, entirely truthful arguments.
How do you know it wasn’t produced by them?
Someone in the FBI would have access to underground CPUSA documents.