I suspect there's a corrupting influence when you call yourself a partisan of an -ism. This self identification can pressure people into dishonesty, because of loyalty to that community.
Though an advantage of anarchism is at least that it's not tied to specific people; that's why it's not called Bakuninism, Malatestinism or something.
Some of the most sensible, knowledgeable criticisms of anarchism I've heard come from within anarchism. So for example, there was an illuminating presentation at an anarchist conference, called "The Anarchism of Fools: Conspiracy Theory as a Substitute for Social Critique." And the first time I heard the term "anarcho-wingnut," it was from a talk at the same conference. (Maybe a different year of the same conference.)
And we'll find terrible opinions from any figure. Take Bertrand Russell, Chomsky's hero. IIRC, Finkelstein pointed out that Russell had pretty bad views concerning Arabs in Palestine. Did that invalidate the overall importance of Russell's views? I doubt it. But I would raise an eyebrow when confronted with a self-described Russellist, just as anyone would with a "Newtonite."
Tayssir